In brief: A friend of my partner was in a relationship with a woman for around 8 years. She already had a child and they had a child together.
Shortly before they split up his girlfriend's sister had a baby girl, so she was around 4 months old when they separated.
3 years later, this friend saw the sister whilst shopping and cooed over the little girl, saying 'he'd missed her'
(even though he hadn't seen her since she was 4 months!)
The mother of the little girl then said ''oh you can have her on Saturday if you want, I've been invited out and can't get a babysitter?''.
So on Saturday, the little girl arrived at a strangers house (granted her 9 year old cousin was there) and the little girl slept in the double bed of this man...
AIBU in thinking it is totally irresponsible of A) the mother for allowing her daughter to be looked after by a man she only knew through having a relationship with her sister and B) him for putting himself in what could be a 'dangerous' situation?
I certainly wouldn't be packing my child off to a virtual stranger so I could get out.