losing the plot
dear Baker, situations like this are always difficult to cope with, especially when someone is 15 as they are heading towards adulthood.
There are different factors here to consider, whether your kids get on with his kids and their relationship is worthwhile staying, and the main one being, if you love your partner enough to stay with him, but if it's only mediocre then maybe you should decide to move on.
You have to remember if you stay, his son is always going to be there in the background, and your partner will give him privileges which you won't agree with. Geoff. x