Need advice please

How do you form an emotional attachment to your S/o child?

I don’t have any kids of my own and I’m trying to FEEL something motherly towards the child since I take care of them when they stay with us and they are only 5. I’m trying not to be stank or have an attitude but sometimes I just get aggravated with the child and the infatuation he has with them and the fact that me and him never get ANY alone time period and they get extremely jealous when he shows me any type of affection so he doesn’t and it just leaves me out.

Please no judgement. Just asking for advice.