I don’t know how much lee-way to give him for not being more forthcoming with this information.
————-
It depends on whether or not this is a serious relationship (likely heading toward marriage or raising children together). If you only started dating in the past few months, and haven’t had a “money” conversation, then it’s certainly something to watch, but not end the relationship over it.
OTOH, if you’ve talked money, or child support, etc. and he’s never mentioned this stuff to you, it’s time to leave, IMHO.
Another thing to keep in mind is that what he does to his former spouse/mother of his child, he’ll be willing to do to you. Once a cheater/liar/thief, always a cheater/liar/thief.