The inlaws would like a word to help us define our relationships. Is there a name for the relationship the parents have to each other? We are more like sisters than inlaws. Explaining the marriages makes your brain explode so we'd like to find a short name to tell the story more succinctly. My daughter is her brother's cousin in-law. My son is his sister's cousin in-law. My daughter's mother in law is her brother's aunt. My son's mother in-law is his sister's aunt.