We have 3 DC (DS 2, DS 4, & DD 7).
DS (2) has his cot bed in our room (it's temporary, we're moving to a bigger house soon). DS (4) shares a room with DD (7) but wakes up in the night and gets into our bed. He has always done this, we tried putting him back for a while but he just got so upset and woke DD up so we just let him. He's small and doesn't fidget so it's not a problem for us.
When DD was a toddler we were much stricter and she was always put back into her bed as she would fidget, she is now a perfect sleeper but she does get upset that she ends up on her own in her bedroom and the other two are 'allowed' to sleep in our room... Is this really unfair on DD?