When is it ok to let siblings sleep together do you think?

DD1 (3yrs) doesn't cosleep any more, she sleeps in her own room and has since she was about 2. DD2 (1yr) sleeps with us still. But every now and then DD1 will just come to bed with us when we go to bed, for a special treat coz it's so nice snuggling up. Or sometimes she might wake really early in the morning and come and hop in bed with us. DD2 sleeps in her cot until her first wake up so if we have DD1 in there DH will move her back to her bed when DD2 wakes because we are worried it's unsafe for her to sleep with DD2. She might roll on her or something.

I was just day dreaming about how cute it would be to all snuggle up together in bed, lol. Is DD2 old enough for that now or is it dangerous?? They would have to sleep next to each other in the middle or else they'd fall out. It would probably be too squishy anyway and they would get annoyed at no space but how cute would it be!! lol.

Just pondering I guess... I think I should go to bed and stop rambling lol.

Does anyone cosleep with more than one child? Or even do you have kids that cosleep together without you? (omg cuteness!)