good idea or bad idea?
Timmy liked Nick to sleep in his bed, my only worry is Tim's a wild sleeper. Actually so is Nick. Im just worried Tim might roll over on Nick or something.
Tim's bed has bumpers so Im not really worried about him falling out of bed, he cant put himself into a sitting position yet and doesn't roll from his back to stomach yet either.
Re: siblings sharing a bed
Not at this age. When DS is older 4ish I may consider letting him have bed sleepovers with his cousin, 2 years older.
I don't trust DH to sleep in bed with DS! He rolled over on me the other night and had no clue he did it.
That's how I feel. I usually just move Nick into his crib after they fall asleep. And we don't do it ever night. H and my (lovely) MIL think Im crazy for being paranoid about it.
We'll miss you sweet Debbie Girl (4.21.12) and sweet Cindy Girl (8.9.12)

I agree.
Jess & Adam, married 2009, precious Audrey born in 2011. BFP 1/6/13, 6-wk MMC discovered at 9 wks 2/11/13. D&C 2/18/13, second D&C 4/23/13 for retained placenta.
BFP 8/24/13!! EDD 5/1/14, delivered healthy and sweet Zoey Leanne on 5/5/14 by repeat c-section.
You're definitely not paranoid. Just stick to your guns. :-) Why is it MIL have the best opinions?