Yeah yeah yeah, all boys and men are potential abusers and all girls and women therefore are manipulative bullies. Why not go the whole hog for the stereotypes eh?
I read page 1. Yes there were comments that implied the 10yr boy was a potential abuser with one poster saying it was a child protection issue.
No doubt there are stories from both sides about how someone was abused in similar circumstances and other stories about how children of all ages snuggle up perfectly happy and innocently every night.
The boy is NOT related at all, in any way, to the girl.
They have a spare room.
They have a spare bed.
Regardless of stupid and pointless stereotyping and tragic experiences related by all - this boy has a perfectly decent bed of his own and could have a perfectly decent room of his own. He is not related to the girl and so under the circumstances he should not have to sleep in the same bed as her.
I understand he might want to and so might she. I used to call my younger brother into my bed when I was 12 and he was 9 because he was cuddly and warmed the bed up. My experience does not relate to this one however as we don't know either of these two children. We know nothing about the adults involved or the set up, we only know what we've been told in a couple of posts from one person's perspective.
I suggest the OP has a friendly chat with both the dad AND his girlfriend. She can then explain her feelings and ask them to explain theirs. Her worries are justifiable as this is her daughter after all and she doesn't know this boy. Some 10 year olds are lovely and innocent and playful and others (I've worked in a primary school) are sexually inappropriate, aggressive, stubborn and vile.
The mother needs to stop arsing around on Mumsnet and take control of this situation. She's had more than enough advice now. She isn't being unreasonable to have concerns and the father is being unreasonable if he refuses to acknowledge those concerns.
The girlfriend will be protective over her brother of course and the father wants to please the girlfriend, but this little girl and the little boy need their own space and should not put in a situation that causes anxiety and worry to others. Especially if that situation is an unnecessary one.