My daughters are 13 months apart and when Belle grew too big for the bassinet, we were going to move her into her sister's room. We started putting them together at nap time for a few days, and neither one of them really cared for it.
Instead, Kaia would go and sleep in my son's room, who's six. We asked him if he'd mind sharing a room with her, and he said he'd give it a shot. We went out and bought them bunk beds and they LOVE it. Having Kaia in Caleb's room has really helped solidify her sleeping habits. She used to go to bed at all different hours, but now she's on his schedule and we have NO fuss from her (which is great from an 18 month old!) :P It also gives Belle a chance to make her own bedtime routine and get used to us not being in the room with her.
I'd just see how they do together, and if it doesn't go well after a few weeks, give them some space till they're a bit older. I think it really just depends on your children's personalities. Congrats on #2!