I think in the 1st episode it was explained that one of the boys was his and the other 2 where hers.Jayjoans said:None of the kids looked like they had the same parents, and none of them looked like really either of them. Maybe he is a 2nd, 3rd, 4th husband who brought one or more kids into he marriage and not really that well integrated with her or the other kids.
Get that little girl outta there Dad, I hope they had a long talk with her afterwards and helped her through it.