All you go to do is keep Ralph out of the kids life for the first 10 years, Ralph will be dead by then. Probably sooner.
To Ralph, the subject of kids is of course, all too real because it occupies his mind often - there are R.O.s, court matters and child support. I'm sure every day he spends a great deal of time thinking about them. But he is confused as to where he really stands.
What Ralph has to come to terms with is back in the homes where his children are, they are being raised by other adults, enjoying life, forming bonds with the grandparents and will frankly, have closer ties with babysitters or the neighbors than they ever will with Ralph. Ralph is not even a memory in the children's minds to be replayed. He is a nobody. In Ralph's demented, TV packed, white trash mind he envisions some day himself as a new man rolling up to a house and a little child comes running up to him, with embraces and a "Daddy I love you!!!". Ralphs hopes are gossamer threads. That will never happen. Ever.
He isn't discussed, he isn't seen, and moreover, he isn't thought about at all except by the guardians of the poor mothers and their children who ensure the barrier is up so he can't filth their lives. As a parent you are truly dead to your kids when you don't even cross their minds, and they never think of Ralph. Blippy on the iPad is more real to them, gets a smile from them and arguably, a better father. Certainly Blippy's videos are OK for kids, can you imagine watching a rage pig on the killstream and say "Thats your daddy, isn't he a nice guy?".
They are very real to Ralph, but to them, he doesn't even exist. If he ever does get to see them, it is so brief it is more akin to visiting a mental patient in a Sanitarium where the kid has to see this weirdo who is unusually nice, all the while being watched like a hawk because he is a danger and must be supervised.
"I saw a fat dwarf today that gave me a toy" is about as much as he will ever amount to in terms of a memory, on par with a gift from a freak at the circus. There are kids out there with daddy's in prison that have better family dynamics than Ralph. The only "Daddy I love you" he is going to hear is from the Gimp in Mexico he pays - Or Nick Fuentes.