This is kinda funny, but I have a 3 1/2 year old girl, twin 1 1/2 year old boys and a now 6 month old girl. The 3 1/2 year old and 6 month old share a room right now and have absolutely no problems. Both are good sleepers though. However, when my 6 month old was 2-4 months old, we were living in a temporary furnished apartment with only 3 bedrooms, a small living room and a kitchen. We only brought a basinette for the baby because there wasn't room for a crib. The basinette wouldn't fit around the furniture in my 3 year old's room, so we ended up having the baby sleep in the living room for the 2 months we were there. She didn't wake anyone up (except me) for midnight feedings during that time, then when we moved into the place we're in now, she moved right into the 3 year old's room. Since she's sleeping better through the night, they really don't keep each other up. Usually, one is asleep before the other and they both end up asleep all night. So, you might try having a basinette in another room until your baby sleeps a good amount of time at night, and then move them into the same room together. Maybe put the empty crib in the daughter's room from the start so she'll know what's coming. Hope this helps.