<human>: Since being pregnant and after having my daughter, I've started to get anxious about the idea of my mums partner being left alone with her when they are babysitting. He is difficult to describe as a person, but there is something about him which has always given me the creeps. 

They have been together for over ten years, but my brothers and sisters and I have always felt there was something not quite right about him. The only real example I can give which confirmed his creepiness was when I was still living at home with my sister who was 16 at the time. She had gone to her prom and I was in my room when I heard her come home at about midnight. I then hear my mums bf start talking to her as she comes in the door, he had been sitting there in silence on his own. He starts asking her if he could take some photos of her in her prom dress and tells her that my mum had asked him to. I can hear my sister trying to ignore the subject and go to bed, he then follows her up the stairs and again asks for photos. She says no and he finally leaves and goes downstairs. I asked my sister about this the next day and told her to ask mum about it, she told me she spoke to our mum who confirmed that she had asked him to take photos but I know this can't be true as my mum had taken photos before my sister had gone to the prom. 

We have never spoken about it since and I know it is only one incident but it has stuck with me ever since. I do not trust this man with my daughter but I don't want to stop my mum from looking after her grandchild, I honestly cannot think of anything I can do. I worry that maybe I'm being completely irrational but my instincts are telling me to be careful of him.

Can you condense the text into a few key points?
<bot>: Mums BF tried to take photos of my teenage sister and now I'm scare of leaving my daughter alone with him, but I don't want to stop my mum from looking after her granddaughter