Actually I have had a situation where a caregiver that was with an agency put her own child with me for 3 months using a space I had open due to maternity leave because she was able to take another agency infant. Once her own child turned 2 she took him back and that was fine because I knew upfront what the plan and reasons were. It was in her best interest to do that since it had been a long time since the agency had any children to place and she didn't want to go to the bottom of the wait list for the sake of 3 months.

I also know of caregivers that have put their own child into a dayhome 1-2 days a week as a way of getting them ready for school and separating from the parent, learning to follow directions from another adult, make more friends, etc. so it is more common than you might think.