Liam Cooper arrived in Los Angeles following the death of his mother, Kelly Cooper, who said he could find his father at Forrester Creations. Computer tech Liam, who also interned at Spencer Publications, accidentally recorded Steffy Forrester's conversation about Brooke Logan's sexual encounter with Oliver Jones. Liam's supervisor, Justin Barber, added it to Steffy's video tribute to Brooke as a way of helping his boss, Bill Spencer, Jr., regain control of Forrester. Brooke's husband, Ridge Forrester, was about to punch Liam for his part in it when Liam blurted out, "You're my father!"
Ridge denied knowing Kelly, but Ridge's brother, Thorne Forrester, had dated her; so had Bill, so Bill and Thorne agreed to take a DNA test. Bill and Liam were less than thrilled to find out they were related. However, Bill's wife, Katie Logan Spencer, encouraged them to deepen their father-son bond, as did Hope Logan. Liam developed a sweet romance with Hope, who was recovering from former boyfriend Oliver's betrayal. Steffy, who had been blamed for the video, tried unsuccessfully to seduce Liam away from Hope.
Bill threw Liam a big coming-out party, where Liam got drunk after a misunderstanding with Hope. Social climber Amber Moore lured Liam to her house, where Liam fell and suffered a concussion. He woke up in Amber's bed, but couldn't remember if he and Amber had made love, as she claimed. Amber was actually pregnant by Oliver, but her mother, Tawny Moore, saw a golden opportunity if Amber would claim that Liam, the rich son of Bill Spencer, was the father.
Liam and Hope broke up and made up with dizzying frequency as they were torn between their love and wanting to do right by Liam's baby. Amber dug her heels in, while Oliver tried to win Hope back. While lighting a pilot light in Tawny's trailer, Liam was caught in an explosion and suffered a second concussion. Bill was convinced that the explosion had been Amber's attempt to kill Liam and hatched a failed plot to protect his son by offing Amber.
Liam insisted on being there as his child was born. But when Amber gave birth to an African-American baby, she was forced to reveal that she had also slept with Marcus Forrester. Liam raced to the Big Bear cabin, where Hope was considering Oliver's marriage proposal. Overjoyed that they were free of Amber, Liam and Hope reunited, leaving Oliver in the dust.
Hope wanted to remain a virgin until her wedding night. Liam had understood, but he became frustrated once Hope layered abstinence messages into her Hope For The Future fashion line, so he publicly proposed to Hope at its showing. She privately accepted, but her family wanted her to delay the wedding because of Hope's stance in the media. Meanwhile, Steffy, freshly rejected by Liam's father Bill, slipped in her bathtub. Liam happened by to return Bill's key and saved Steffy from drowning, prompting Steffy to fall for Liam.
Liam confided in Steffy, who let him know she was sexually available and told Liam that Hope was wrong for him. When Hope stopped by to tell Liam she was ready to move in with him, she spied Liam and Steffy kissing in a limo. Hope left her engagement ring on Liam's mantel and broke things off in a cell phone message. Confused, Liam found Hope's ring and put it on Steffy's finger instead.
Steffy sensed that Liam would go back to Hope if he had a chance to talk to her. So Bill sent Steffy and Liam to Aspen, Colorado, where they could be alone. Hope found out and made a beeline for Aspen to clear things up, but Bill was one step ahead and arranged for Hope to be trapped in a gondola above the ski slope, forced to watch as Steffy appeared in a wedding gown and exchanged vows with Liam.
Back in Los Angeles, Liam and Steffy enjoyed life as newlyweds, but Liam was still thinking about Hope, so Bill concocted a "family vacation" in Cabo San Lucas. Since Katie refused to travel with former rival Steffy, Liam and Steffy went alone. Coincidentally, Hope, who was spending time with Thomas Forrester, found herself at the same Mexican resort. Steffy and Thomas hustled to keep Liam and Hope from seeing each other, but the attempt backfired, resulting in an ATV chase in which Steffy was seriously hurt.
Seeing that Liam was ready to return to Hope, Bill faked Steffy's MRI so it looked like she had a brain injury that could kill her. Liam felt obligated to stay with Steffy, even after Steffy confessed about her deceptions in Aspen and Cabo. However, Katie got suspicious and eventually uncovered the extent of Bill's machinations. Bill locked Katie in a tower to keep her from telling Liam, but when she escaped and exposed Bill, Liam had finally had enough of his father's smothering and washed his hands of him.
With Steffy healthy again, Liam asked her for an annulment. Steffy refused to invalidate their marriage and insisted they file for a proper divorce. Hope balked, so her brother Rick Forrester used his past romance with Steffy to sweet-talk her into signing the annulment papers. Believing Rick had succeeded, Brooke arranged a wedding for Hope and Liam that was ultimately halted when it turned out Steffy had written "loser" in place of her signature.
Hope relaxed her stance on waiting for marriage and moved in with Liam to take her power back from Steffy, but froze up in bed. Brooke took Hope to Dr. Stacy Barton, who gave Hope a small supply of antianxiety medication. Liam and Hope finally made love. But when a disgruntled fan of Hope's snapped a photo of them in public, the media branded Hope an adulteress. Liam seemed unaware of Hope's increasing dependence on the pills, even after he saved her from nearly drowning in the Forrester pool. Liam was surprised when Hope told him about her therapy and the pills, but believed her promise that she would stop taking them.
Liam made up with Bill, who resumed trying to control him, while Steffy vacillated between giving Liam space and enticing him to return to her. Liam covered Fashion Week in Aspen and took Hope there to get her away from the paparazzi. Instead, on Bill's orders, the photographers hounded Hope, who downed more pills. By the time she and Liam hit the slopes, Hope was so strung out that she barely noticed crashing into Steffy, who was in Aspen promoting her new ski line. Furious, Liam stayed by Steffy's side at the hospital, newly drawn to her.
Liam confronted Hope and reminded her that he'd left Steffy because of deception. Hope gave Liam the pills, and the couple embraced. Meanwhile, Steffy had a change of heart and signed the annulment papers. Liam was surprised when Hope returned to Los Angeles alone, but stunned when Steffy presented him with the papers. After reminiscing with Steffy about their marriage, Liam took the papers and tore them up.
Again in Los Angeles, Hope decided she'd feel better if she moved out of Liam's house until after their wedding. Liam admired her newfound strength, but kept mum about the papers. Brooke overheard Steffy talking about what had happened in Aspen and confronted Liam, who said he just wanted to be respectful to Steffy and wait for the divorce to go through. Liam begged Brooke not to tell Hope what he had done. Brooke agreed and began planning an Italian wedding for Hope and Liam.
As the days counted down for Liam's divorce to become final, Liam pined for Steffy the way he had formerly pined for Hope. Steffy encouraged Liam to marry Hope anyway. But on his wedding day in Puglia, Italy, Liam thought Hope had left him when he found a note saying she couldn't go through with it. The furious Liam kissed Steffy, told her he loved her, and made plans to fly back to Los Angeles with her on the Spencer jet. But Liam didn't know that Bill had sprung Hope's father, Deacon Sharpe, from jail, and convinced Deacon to distract Hope in order to manipulate Liam back into Steffy's arms. Hope showed up and explained how she had finally met Deacon, and Liam married Hope after all, continuing to be torn about Steffy.
Liam had accidentally recorded footage of him and Steffy kissing in Italy. When Hope saw it, she refused to sign the papers that would have legalized their Italian wedding. Instead, Hope insisted on a fresh wedding. The night before, Steffy "kidnapped" Liam to a club to show him how fun his life could be without Hope. A hung over Liam showed up for his wedding sporting dyed hair and a tattoo. Hope told Liam he didn't deserve her and ended things. Liam, still in his underwear, begged Hope on his knees, prompting Bill to rage at Liam for not living up to the Spencer name.
Unbeknownst to Liam, his efforts to square things with Hope were further thwarted by Hope's brother, Rick Forrester, who convinced his DJ friend Othello to lie that he had seen Liam and Steffy being passionate at the club the night before the wedding. Rick also worked to push Hope toward her step-brother, Thomas Forrester, and Liam was upset to see Thomas kissing Hope. Liam briefly heeded Bill's advice about being a Spencer and treated his employees badly, which confused both Hope and Steffy.
Liam felt pulled toward Steffy, but made another attempt to reunite with Hope after Katie almost died giving birth to Liam's half-brother, Will. When Hope gently refused, Liam sought out Steffy, who took him to a "secret cabin" on Brooke's property, where the two made love. Donna Logan saw Liam and Steffy's lovemaking and reported back to Bill and Brooke, while Liam and Steffy basked in their reunion.
Liam planned to take Steffy to Hawaii, but Bill commandeered the Spencer jet to look for Katie, who had disappeared during a bout with postpartum depression. Liam and Steffy ended up in Aspen with Bill and Brooke, where they found time to go parasailing once it was clear Katie wasn't in the resort town. Upon returning to Los Angeles, Liam asked Steffy to move in with him. She agreed, but said she also wanted to keep her loft. Liam's cousin Caroline informed him that Hope still had feelings for him, but Liam insisted it didn't change things with Steffy. Liam took a business trip out of town, unaware that Bill had arranged it to keep Caroline from revealing what she knew about Bill using Deacon to sabotage Liam's wedding in Italy.
Liam punched Rick when he found out how Rick had Othello lie about Liam and Steffy. But Liam was floored when Hope discovered Bill's deception in Italy and revealed it to Liam. When Liam told Bill he was done with him, Bill stabbed himself in the chest with his sword necklace. A shocked Liam recanted, unaware that Bill had only stabbed himself in his money pouch in an effort to further manipulate Liam.
Steffy had to go out of town and enjoyed a night of lovemaking with Liam before departing, but Liam found himself again intrigued by Hope, who had become more direct in her intentions to win Liam back. Liam kissed Hope; Steffy, whose pregnancy test had just turned up positive, witnessed it. Liam was confused when Steffy told him to get Hope out of his system in her absence, but he swore he would stay loyal. Liam spent a lot of time with Hope, who insisted that Liam should ask Steffy to move out so he would better be able to choose between them.
Liam wanted time to think things through, but Brooke forced Liam's hand by surprising him and Hope with a wedding, even flying in the priest who had officiated at Liam and Hope's Italian ceremony. Liam got caught up in the moment and was about to put a ring on Hope's finger when Steffy arrived and announced she was carrying Liam's child. Liam considered his options, but ultimately chose to make a home with Steffy and the baby. Steffy told Liam she only wanted him by her side if he was absolutely sure that's where he wanted to be. Liam responded by proposing to Steffy, though Steffy didn't know that Hope had insisted Liam marry Steffy before the baby's arrival.
Liam was surprised when Taylor and Eric offered to host his wedding to Steffy at the Forrester mansion (ironically, where Liam had attempted to marry Hope the year before). Liam smiled as Steffy rode into the Forrester courtyard on a motorcycle, wearing a black dress/suit ensemble that Eric had designed. At the reception, Liam brought in Steffy's "all-time favorite" singer, Julia Michaels, to perform. Liam whisked Steffy away to Aspen for their honeymoon, where they discussed possibly naming their child Aspen in honor of the locale. Liam received a text from Hope on his wedding night, but for once, he didn't seem to be bothered by it.