why do people hurt others

for many years now i have been wanting nothing but acceptance form so many people,but for some reason whenever i get close they mess it up by intentionaly and unitentionaly hurting me or my family.

This morning i got a text from them and thbey want to see the baby and give presents to us. I am affraid that if i let them into my life and esspecialy my childrens lives that they or i will be hurt. i am sick or wantting the relationship that is never going to be possible but to what extent to i allow it in my childrens lives? i just want to not have to worry that we are all going to get hurt again and again.