We’re booked to go on holiday with SIL and BIL, self catering holiday cottage. They’ve now said SIL brother may also come. We have a 4 year old dd and a baby, I’ve never met SIL brother and neither has my DC, aibu to say I don’t want him coming? And how would I even say that? I don’t feel comfortable with him staying in the house with my young dd when we don’t know him. I know he’s SIL brother but I don’t think that changes anything for me.