Christopher and Lorelai have known each other since age six. They were best friends growing up. Like Lorelai, he came from a privileged family but was unhappy with the life his parents had planned for him. Rather than go to Princeton as his parents wanted, Christopher wanted to travel through Europe with Lorelai after high school. When Lorelai became pregnant, Christopher agreed to get married and work for Richard's company, as their parents wanted; however, Lorelai refused. Lorelai raised Rory alone, and Christopher had limited contact with his daughter.
In Season 1, Christopher comes to Stars Hollow for the first time (1.14). He stays with Lorelai and Rory, and he asks Lorelai to marry him, but she refuses (1.15). Although both his father and Richard brag about Christopher's business success in California, he confesses to Lorelai that his business is in serious financial trouble.
In Season 2, he returns to Stars Hollow to present Rory at her debutante ball (2.06). He is now living in Boston with his girlfriend Sherry Tinsdale and has a good job. At the end of Season 2, he is unhappy with Sherry, and he and Lorelai sleep together at Sookie's wedding. Also when Rory and Jess crashes Rory's car (2.19), causing the accident that fractures her wrist, Christopher is the person Lorelai calls after seeing Rory's damaged car, and he stays with them for a couple days. However, when he learns Sherry is pregnant, he goes back to her (2.22). In Season 3, Sherry gives birth to their daughter Georgia, nicknamed Gigi (3.13). 2 years later Sherry leaves him and Gigi to take a job in Paris (5.06). Christopher repeatedly turns to Lorelai for help with his daughter.
Christopher's presence in Lorelai's life puts strain on her relationship with Luke Danes. Lorelai stays over at Christopher's house the night she and Rory find out from Richard and Emily that Christopher's father, Straub Hayden, has died, and the both of them drink tequilla all night long, but have no sexual interaction whatsoever (5.11). At Emily's urging, Christopher attends Emily and Richard's wedding vow renewal and begs her to get back together with him (5.13). Lorelai is furious with both her mother and Christopher, and they don't speak for several months. They get back in touch when Christopher wants to financially provide for Lorelai and Rory, and they agree he'll take over paying Rory's tuition at Yale (6.10). After Lorelai and Luke break up at the end of Season 6, Lorelai spends the night with Christopher, and they begin a relationship in Season 7. After accompanying Gigi to France to see her mother, Christopher and Lorelai spontaneously get married, and Christopher moves into Lorelai's house in Stars Hollow. However, Christopher continues to be very jealous of Luke. After he finds a letter that Lorelai wrote for Luke's custody battle, Christopher questions whether Lorelai really loves him (7.12). When Lorelai's father has a heart attack, Christopher is upset to see Luke the hospital (7.13). Lorelai considers cutting Luke out of her life completely to save her marriage, but a conversation with Sookie makes Lorelai realize that their relationship isn't right (7.14).