I read a book as a kid and I am trying to find it for my nephew. In it, an infant is stolen by aliens and kept as a pet, and the older sibling(s) go on a rescue mission. I don't really remember much else about it.
I must have read it in late elementary school, so probably around 20 years ago. The scene that sticks in my mind is the older children looking through a window and seeing the baby sleeping.
I don't remember the aliens being malicious so much as indifferent.
I've been looking for this for a while, so if anyone can help I would really appreciate it.