I saw Lesley Sharpe, who plays Jack's mum Anne, on This Morning and she explained the drama is based on the writer's observations of how modern family life now is.
So many couples break up and form new relationships, taking on new families. Parents in the 40+ age group are selfish, wanting to lead their own lives and shirking their parental responsibilities for their own children in favour of their new family unit.
I've seen it happen with my partner's brother. He split from his first daughter's mother several years ago and has another child with his current partner. The first child rarely gets a look in anymore.