What's the difference between "surrogate" and "someone-in-the-law"?
A "surrogate" is someone who plays a substitute role for someone else. In this case, a "surrogate mother" means someone who will, using someone else's egg, give birth to a child for someone who cannot. This has become more common recently as technology has improved. It is a completely different concept to in-laws, who are relatives connected by marriage. Ex: Many people who suffer from fertility issues will seek surrogate mothers. Ex: Surrogacy is becoming more common in recent years.