Jeff Isaacs is the father of Toby Isaacs. He was formerly married to Anne Marie Isaacs, and has since been re-married to Kate Kerwin and is the stepfather of her daughter, Ashley Kerwin. He was portrayed by Nigel Hamer.
First seen touring the new school with Toby in the first Degrassi: The Next Generation episode, Mother and Child Reunion (1), Jeff Isaacs has made a number of appearances throughout the first season of the series.
Though a loving father to Toby, he and his ex-wife Anne Marie cannot have a conversation without it turning into an argument.
After splitting up, he and Toby move in with his new wife, Kate Kerwin (Ashley's mother), which causes some friction between Toby and Ashley.
In Parents' Day, the relationship between him and his ex-wife is revealed. It is apparent that they cannot even be in the same room as each other without arguing and as they were meeting for their son's parent-teacher interview, Jeff promises Toby that they will have no arguments. Toby is worried, considering his mom's attitude.
However, even though Jeff tries not to engage his ex-wife further during the interview, he eventually falters and joins Anne Marie in an escalating argument.
Jeff takes a strong stance that Anne Marie breaks her commitment to their family to instead, pursue her casting career.
The specific reason for why they separated is unknown but its revealed that it was Anne Marie left, who also cites that threats are "Jeff's area of expertise."
In the episode Secrets and Lies, when Ashley comes home from being dropped off by her father, she walks in on Jeff and Kate arguing over doing the dishes.
When the argument is seemingly about to be escalated by Jeff, he sees his stepdaughter and simply jokes that Kate was in "one of her moods again."
Even though it seemed their relationship may have been faltering and deteriorating into Jeff's previous relationship with his ex-wife, it was not the case as they both still share a strong and loving bond.