Your daughter is 11 you have the right to block any buddies that you feel is not a good influence on your daughter she is underage he’s older age it doesn’t sound right to me I would start checking the messages that he’s sending her and if anything is improper I would call the police and then I would proceed from there
I find it very strange he is acting that way with her being a mom of girls its something i would keep my eye on maybe he just got a strong bond but you can never be to careful and i dont know the full story or what all went on but if you feel like you need to protect your little girl then do what is needed
Can’t you block his number?