I feel sorry for the children...

They are my boyfriend's children.He has 3 kids 4,1 and a 2 months old baby girl and their situation right now is something that bother's us a lot me and my boyfriend.His ex live in partner is going crazy and what she's doing with the kids can be very traumatic to them. She found out about me and now she's like usng the kids to get my boyfriend's attention.They already had an understanding in our local city government about how the should deal with the children's needs.They both agreed upon it but ever since she found out about she started acting crazy and confront my boyfriend infront of his house shouting and scandalous.To my understanding she was jealous about and now she keeps on going back and fort with the 2 months old baby even on a rainy evening. She will go to his house give the baby to him without the baby's clothes and say she's giving the custody to my bf and each time that he accepts his baby girl with full responsibility she will suddenly change her mind and will get the baby again when bf is not around..I dont know what was she thinking but what i only know is she's not being reasonable..the children's needs is never neglected! I feel sorry for the kids because they might grow up feeling they are unwanted because one day their with their father the next day she'll get them back and then give it away again to their father. I dont know what kind of mentality is that? but she's giving a psychological effect to her children that i cannot get involve with...which makes me feel sometimes I wish I was the mother of her children..