I'm surprised by most opinions in here. Bunch of politically correct answers...
Of course he is justified! He surely loved your mum when they got married, but now that has obviously changed. He still appreciates her as a person and he surely feels pity for her and he also doesn't want you all kids to suffer. I'd say he has been sacrificing a lot. Give your old one a break!
Your parents are not freaking perfect. They are human beings. They have the right to be happy.
If you want some advice, just support them, talk with them and be prepared because they may get divorced soon, but it doesn't mean that they hate each other or that they can't be friends. Relationships eventually end and there's nothing wrong with that. Don't be selfish. As long as they take care of you it doesn't matter who they shag.
Of course he is justified! He surely loved your mum when they got married, but now that has obviously changed. He still appreciates her as a person and he surely feels pity for her and he also doesn't want you all kids to suffer. I'd say he has been sacrificing a lot. Give your old one a break!
Your parents are not freaking perfect. They are human beings. They have the right to be happy.
If you want some advice, just support them, talk with them and be prepared because they may get divorced soon, but it doesn't mean that they hate each other or that they can't be friends. Relationships eventually end and there's nothing wrong with that. Don't be selfish. As long as they take care of you it doesn't matter who they shag.