Tell him to see you in court and serve him child support papers. Kids learn attachment styles and how to develop relationships by their parents. Absent parents can lead to insecure attachment styles that will impact them for life. Don't let your kids see their father treat you like a doormat either.
Do it legally.
legally or with social services / cafcass, professionals etc. then it’ll be in black and white and you won’t be messed about or stressing about anything and they can take care of it :)
Let him.
go through the court system and put him on child support with a custody arrangement in place. if he wants to be in the child's life, then this is the proper way to do it.