My three all sleep with us at night. When I introduced a new "little one" we always kept them zippered into a travel kennel between our pillows (we have a king size bed). They each had their own blanket and soft toy. It gave the babies a chance to see/smell their pack members, but kept them safe from falling out of bed. They also did not have the opportunity to disturb their big brother(s). They would settle right in, but we could hear them if they needed a potty break. A quick trip to the potty pad if needed, then zipped back in.
When they grew big enough to trust on their own, we began to leave the zipper door open. They would usually sleep inside for some of the evening, then venture outside to settle in with one of the other dogs at first. Now they each have a small cuddle cup bed on our bed, and sleep in a row between us.
The added benefit of training them in their small travel crates is that when we are "on the road" to visit grand kids, they will happily sleep inside if the occasion calls for it. They are soft-sided, zip inside each other to store, and everybody still has their original baby blanket and toy.
