Consistency is key. Continue each child’s bedtime routine as before—perhaps bath, lullaby, and feeding for baby, and a bath, book, and goodnight cuddle for the older sibling. Stagger their bedtimes, with baby going to sleep first so your older child has a little extra time with you. Explain to her that you may be coming in and out of the room to feed the baby, but that she can stay in bed. (Young children are heavy sleepers, so it takes a lot to wake them up.) For insurance, use a white noise machine so sudden sounds from either child don’t bother the other. After a period of adjustment, each child should be able to tune out the other’s regular nighttime noises. And with time, you’ll find that sharing a room can bring the two closer together.