I am divorced but this was an issue when I still lived with exH.
He used to let the children (I’d say encourage but maybe I’m being mean), sleep in his bed.
i always used to try and get them to sleep in their own beds as much as possible.
(we are from different cultures, not sure if relevant).
anyway, fast forward to now, my 6.5 year old daughter spends every night in her uncles bed when she’s at her dads. My 8 year old son has his father sleeping on the bottom bunk every night. When they’re at mine they sleep in their own beds, every time, unless they wake upset in the night, which is very rare).
totally happy to be told I’m being unreasonable but I really find it a bit ‘icky’ and uncomfortable. Hoping that I’m told I’m wrong and that I don’t need to bring it up with them. (Definitely don’t think anything untoward is going on with uncle - at all, I really just think it’s inappropriate and a bit engulfing/smothering of the dad and brother to be allowing this).
YABU - it’s fine for the kids to do this when little
YANBU - they should be in their own beds