Does this person really care about his child or somewhat obsessed with his ex and baby mama?

My 7 yr old step sisters 19 and 15 suddenly want to see her after showing no interest in 3 yrs. I am somewhat apprehensive at letting them around my child because of something that the 19year�did to leaf me to believe that their desires to see her is not sincere.�You see their father my ex and I are not on speaking terms( boundary issues) �come to my house on the pretense of seeing our child unannounced and call the land line and not leave any messages, and still trying sleep with me though married. Got a prepaid phone for my daughter # given to him to contact her directly. �He called twice 1) apologized when his older children called the 7 yr old at 10:30pm and �2)two days later after he was given her schedule when she can use the phone and her bedtime. No other calls since.�Meanwhile, fews days ago, �noticed excepts of a text communication between the 19 yr old with my 7 year old asking some personal information about me and my current fianc�. I told the girl that it was inappropriate for her to do so, she went off on me calling a liar and that I take things too seriously and that I didn't know how to let go of things at all and was overreacting.�My ex was habitually unfaithful, so I left him and not cut him out of my life. �He had gotten very vicious and start spreading rumors about me to the point of causing a rift between me and my family and some friends. When I cut him totally out of my life, he started to deny our child and has not have any contact with her. I don't care what they do, just let me be to raise my child in peace which seems to be somewhat a problem for them. And when his new wife got charged for domestic battery for hitting him in December, he sent his kids when I would not talk to him. I just found out that he was the one answering the text messages that his daughter sent me. What do you make of all of this drama?