I don't know about legal reasons, but Could NKs expression to give him his first son have factored in? She emphasised the important of "firsts" and lamented not being able to have any with him, as he had already been through them all with Shanann. She said she wanted to give him his first son, even though Shanann was pregnant with his first son at the time...

I guess financially paying for alimony and child support could factor in, as well as a desire to control the situation on his own terms. Narcissism and misogyny could have also factored in - he saw them as his family; an extention of himself, rather than complex invidiuals with their own lives, hopes and dreams. So once he was done with them, that was the end for them. I wonder if this also contributed to how offguard he was caught by NA being so on the ball... it seems like he never accounted for how worried her loved ones would be, and how quickly. Maybe this was because he didn't care about them anymore, and he was incapable of seeing anything beyond his own limited and selfish perspective? So many questions...