The relationship between stepsiblings Ashley Kerwin and Toby Isaacs began prior to Season 1 of Degrassi: The Next Generation when Ashley's mother Kate Kerwin married Toby's father Jeff Isaacs.

Sibling history

Season 1

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In Family Politics, Ashley tries to get into her bathroom, but Toby is already in it. They argue and it's discovered they are not biological or even step siblings, but are forced to co-habitate because their parents (Ashley's mom and Toby's dad) are living together. Toby runs out of the bathroom wearing Ashley's bra and she screams for her mom. It's the first day of school at Degrassi, and Toby is complaining about Ashley to J.T. He thinks she resents him and treats him like an unwanted house-guest because he and his dad live in her and her mother's house. On the other hand, Ashley is complaining to Terri about how annoying Toby is while she's putting up her campaign posters. They run into Paige for the first time as she says her classic line "New year, new look, new Paige". After getting out of homeroom, Emma, Manny, J.T. and Toby notice Ashley's campaign posters on the wall. Toby hates the fact that no one is running against her, and he convinces J.T. to run a joke campaign to make her sweat.

He begins printing out fliers and while putting them up he runs into Ashley, who doesn't take J.T.'s nomination seriously. Meanwhile, J.T. begins his campaign, saying he'll do what a real politician would do: "Absolutely nothing!" Ashley starts her campaign as well, addressing real issues such as starting a recycling program and getting the school a nighttime dance. Ashley's frustration begins when she sees that people are starting to pay attention to J.T.'s speeches, mainly because he is funny and the class clown. At home, Ashley confronts Toby for helping run J.T.'s campaign. Ashley's mom walks in and says Toby should be allowed to help with his friend's campaign. Naturally, that upsets Ashley because she feels her mom always takes Toby's side. On the day of the assembly, Toby and J.T. see that J.T. has as much school support as Ashley in the election. J.T. starts worrying that he might actually win.

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While J.T. is at his locker, Jimmy and Spinner grab him and take him to the locker room where Ashley is waiting. Ashley offers J.T. eighty dollars to drop out of the election, but only gives him half of the money. She promises him the rest when he comes through with his end of the promise. Toby finds out about the bribe and is angry because he thinks Ashley gets everything she wants. During J.T.'s speech, Toby confronts Ashley in the hallway. He threatens to tell the school about her bribing J.T., but Ashley tells Toby that he gets all the attention at home and her mom cares more about him. Because she feels Toby has stolen everything she had at home, she wants the one thing that he couldn't take away from her: being school president. In the final scene, Jimmy walks Ashley home and congratulates her on winning the election. Toby is sitting outside and congratulates Ashley too. He apologizes to her and they both realize that as long as they're living in the same house they have to at least try and get along better.

In Jagged Little Pill, Ashley and Toby's parents are going away for a bit and allow them both to invite one friend over each. However, both of them end up inviting more than one friend. Ashley then invites Paige, Terri, and Hazel. Toby invites J.T. and Sean in order to get Manny and Emma to come over. Later, everyone begins to leave besides Toby and Terri. The episode ends with Ashley slumping down the wall, crying. Toby and Terri try to comfort her.

Season 2

In Mirror in the Bathroom, Ashley and Toby's relationship continues to grow when Toby began to use laxatives to make the wrestling team. Ashley saw him using them and he tried to make her not care, but she still did and spoke with J.T. about it. In the end, Toby stopped using them.

Season 3

In Holiday (1), Toby tells Craig Manning that Ashley is home and lets him inside the house.

In Accidents Will Happen (2), Toby was present in the cafeteria when Ashley announced that Manny was pregnant with Craig's child.

Season 4

In Time Stands Still (2), Toby, Ashley, and Emma are seen watching T.V. After the tragic school shooting. Ashley calls Rick a psycho, which upsets Toby. Emma stands up for Rick and surprises Ashley, saying that he was Toby's friend.

Season 5

In High Fidelity (2), Toby greets Ashley by jokingly bumping into her after spending a year in England, and she responds by hitting him on the head.

Season 6

In The Bitterest Pill, Ashley and Toby both attended the Degrassi memorial service for J.T., who was murdered by a Lakehurst Secondary School student named Drake Lempkey several days earlier.

Season 7

In It's Tricky, Toby, along with Emma, comments to Ashley about the songs that Craig wrote about her, saying that he obviously hasn't forgotten about her.

In Bust a Move (1), Toby and Ashley are seen sitting together, discussing their plans for Spring Break.