I don't get the dad.... It's your daughter yes, but that's also your son..?

To me, it seems like Dad never wanted kids but loved his wife a lot. Daughter reminds him of his wife but his sons are just like him so he doesnt care about them. Not very nice but it makes sense esp if hes as antisocial as he seems

Also Dad is clearly depressed at the start of the story and waiting to die, most likely bc of his wife. MC is his new lease on life so shes special to him

You brought up a good point, that makes sense.

He feels no attachment to the children of the love of his life, that's interesting