Unfortunately most men, not all, but most, really don't want to be the lead person in the home.
They don't want to carry the mental load, they would much rather "help", be directed, take zero primary responsibility.
This is hard enough to tolerate if you share children, but to do it for a lazy avoidant man and HIS children, children that are not biologically yours, is truly beyond me.
The teen years are not easy and I am not even talking the hard stuff.
I'm talking mess, tidying up, constant running them places, making sure they are safe, monitoring alcohol, friends, them no longer wanting to eat meals at regular times.
I have great children, all very successful academically, but I have dealt with all of the above.....and I still think I haven't had a particularly rough decade + compared with some.
As you get well into the teen years, you will be beyond grateful that the only child you have this responsibility for, is your own.
It is so easy to see why newly single men will target any soft soul that is prepared to do the very heavy lifting for them.
Indeed watch out he doesn't try to impose with a gift.
Far better he and his children give your son space.