Not much is known about the details or gameplay mechanics about child contracts yet, besides which surname the child will recieve, culture, language(s), etc. Which culture the child is raised in is stipulated in the document between the parents, and who will raise the child. In the scenarios you've provided, it would be possible to carry them out if the child contract was set up that way to raise the child in a Brudvir culture. Specifics by Caspian listed below:
Bloodlines and Raising (06-18-17):
Specifically under #3, discussing family contracts (11-15-17):
Child Contracts (specifically the second paragraph) (02-09-18):