As an adult, Lawrence's son Ferb was born, a very intelligent child with few words to say and green hair. It is not known whether or not Lawrence was ever married to Ferb's biological mother or how their relationship ended, but she is never mentioned and no longer a part of Ferb's life ("Dude, We're Getting the Band Back Together," "A Hard Day's Knight").
While living in America, Lawrence began dating a woman named Linda Flynn. He was very nervous around her, barely ever having been able even to hold her hand. This changed after he obtained tickets to the farewell concert of her favorite band, Love Handel. During the concert, the band's lead singer, Danny, illuminated them with his 'flaming hot spotlight of love', and without anything else to do, he embraced her and pulled her into a passionate kiss. Not long afterwards, on June 15th, they were married. ("Dude, We're Getting the Band Back Together," "Mom's Birthday").
When Lawrence married Linda, he also gained two stepchildren, Phineas Flynn and his sister Candace. Lawrence's personality rubbed off on his two new children, with Linda once stating that they have his imagination. However, it should be noted Linda's statements about the children's imagination usually come from her not believing the things they tell her.
Lawrence works as an antique dealer and historian. therefore, he has a knack for world history, particularly that of the United States. He often references events in history in average conversations. He sells his own items as antiques as well ("Crack That Whip," "Out to Launch," "Get That Bigfoot Outa My Face!", "Just Passing Through").
Lawrence is absent-minded, easygoing, imaginative, and has a childlike innocence about his sons' contraptions. Unlike his wife, he knows that his boys build amazing things and often seems to encourage it. For example, when Phineas and Ferb build the monster truck track to help their sister learn to parallel park, he actively participates. He also was involved riding on the magic carpet.("It's a Mud, Mud, Mud, Mud World", "Magic Carpet Ride"). Other times, he's too distracted to notice if he's preoccupied with other things such as watching movies or telling his old fishing stories ("Greece Lightning", "The Lake Nose Monster").
He is the largest collector of Pinhead Pierre memorabilia in the world. He is sheepishly proud of this fact. When he shows an old episode of the show to Phineas and Ferb, they build their own animation studio in their backyard ("Out of Toon", "Magic Carpet Ride").