Gilbert Blythe is the husband of Anne Shirley, the ex-boyfriend of Josie Pye, and the adoptive father of Dominic. He seemed to be very smart when he was young (we meet him when he's 16) but he's in the same class with Anne, Diana, and Josie. He and Anne have a very bad squabble Anne's first day in class when Gilbert, who sits in the desk next to her, calls her "Carrots" (because of Anne's red hair) and yanks on one of her braids, hard. Anne, who doesn't take too kindly to this because she's very sensitive about her looks, screams, "How dare you?!" and breaks Gilbert's slate over his head. Gilbert tries to explain to their teacher, Mr. Phillips, that he'd been egging Anne on and that it was his fault and not Anne's. Mr. Phillips didn't listen and instead just dragged Anne up in front of the class and made her write "Anne Shirley has a very bad temper" (only he wrote the first name as "Ann" without the E) one hundred times before she was allowed to leave class.
Gilbert tries to persuade Anne to be his friend several times over the years, but fails miserably on many occasions. He apologizes after rescuing her from almost drowning when she's 16 and he's 19. She gives him a "maybe" on the friendship front, and it's not until the end of the first movie that he flirts with her and she doesn't stop him. In the second film, Anne is convinced that Gilbert isn't the one for her, especially after he reveals his love for Anne. After Anne leaves Avonlea to take a teaching job, Gilbert attends medical school and gets engaged to someone else.
When he gets a bad fever, Anne returns home and finds Gilbert ill. He finds out that she dedicated a book to him and that she wanted to give it to him as a wedding gift, but Gilbert tells Anne that there won't be a wedding and that he still loves her. Anne and Gilbert agree to get engaged as soon as Gilbert finishes medical school.
In the last movie, Gilbert is a doctor for a time at a hospital in New York. He finds out about all the conflicts going on in Europe after he and Anne return to Avonlea, and he tries to gently break it to her that he enlisted in WWI with Fred Wright, Diana's husband. Anne is very upset, but Gilbert persuades Anne to marry him before he goes, and they do. When Gilbert is away, he stops writing to Anne and then Anne takes a years-long journey to find him. When she does, she is so joyful. They return home and adopt a little boy named Dominic.