I’d say that you have at least a minimal duty to them until they’re 18, no matter what. Even if they’re in prison for killing your other child, for a really extreme example, you have a duty to ensure that they’re safe and their needs are being met as well as possible. You don’t have to shelter them from the police or anything, and I can understand if you no longer feel love for them, but you’re responsible for getting them to adulthood as best you can.

Of course, I wouldn’t judge anyone actually in that situation for disowning their child (or any number of other reactions that I would consider ethically wrong, but that’s because they’re in a truly awful situation and it makes sense to go a little crazy), but it’s the moral ideal I would shoot for.

I mean, there's a kid who grew up down the street. He pitched for the brewers. When he came outside at four years old and threw his older brother's hamster across the street (to see if it could fly he said, and for a brief glorious second it could remember he pitched for the brewers?) the whole neighborhood apparatus went into play. All us older neighborhood kids, even the gang members and criminals, it didn't matter we looked after and out for him. Like the gang just sold weed. They weren't killing people (much) and wanted to keep it that way. We didn't want another zodiac killer. And he turned out all right. Became a functioning fungible member of society. More than me. Pitched for the brewers and all. So to answer your question it takes more than one animal.

I would disown my kid for being a murderer if it was not for reason of insanity or self protection or otherwise justifiable, yes. Or a torturer, etc. There are certain extreme moral lines that I would have to acknowledge that my child as I knew them did not exist. But they are certainly of the most extreme, it would be very difficult to do so, and it would be very rare circumstances.

Disowning is your own perogative. meaning that you have to make the call.

If your kid does break the law, then you have the social obligation to tell about it.

This is a writing scenario I’ve envisioned in a book (in part because said book needs a villain, and villain bad)

A dad realizes on some level that his son isn’t just “gruff” like he is, but just plain mean and evil, and that none of the moral core he’s instilled has made it in - it’s not even upbringing, just that the kid is hateful and never self-reflective. And for a very short moment, he thinks about violent action.

If you find out that your kid is a monster YOU fucked up. Disowning is cowardice... clean up the mess you made.