Got to pipe in here. Been married 44 years. When we got married my wife had 2 sons, 6 and 10, I had a girl 2. From the day we got married WE had 2 sons and a daughter with another daughter coming later. All three kids knew there was another parent and they visited often. I built a barn and put 80 rabbits in it. The kids took care of them and 50% of the income went to them. They in turn was required to put 20% of their part in a saving account, encouraged to tithe 10% and the rest was theirs. If you treat your son as a step-son, he will always resent it and he demeanor will reflect it.

The crowning moment of time with the kids was when my youngest son (he was 12 at the time) told his biological father that "Daddy lives with Momma, you are my father."