What a cute idea Ginger.
I have never been a mid-wife, much less to a Tin family.
I talked to Lizzy this morning and she said she is pretty naive on the subject, but she said she "thinks" the babies drop out from under her skirt and can be anywhere from infancy to a teenager at birth. Also, they do not grow bigger as human babes do. The only way to gauge their age is by the amount of rust they accumulate over the years.