Bit of a strange question. My son, 3, really likes to sleep with other people, from time to time. I don't think I'd want him sharing a bed every night, because I don't think he'd sleep that well (we did cosleep with him, when he was tiny, and we're now cosleeping with his baby brother, which is probably where the interest comes from). He had a nap with his gran last weekend, which went very well, and was a nice cozy thing for them to do.
He'd like to have a nap with his brother. I know this isn't even vaguely possible, as his brother is 8 weeks old, and DS1 doesn't understand about not putting things over his baby brother's face.
But at what age would you let your kids have a nap together, or sleep together on holiday? I'm thinking maybe when DS2 is 1 and DS1 is 4? By which point DS1 will have lost interest, I'm sure, but I'm still curious.