Hi. My name is also Maria Quintanilla. I was born in the US as well, but my family is originally from Monterrey, Mexico. My father is Pedro Quintanilla Gómez, whose father was Pedro Quintanilla Coffin (who was at one time mayor of Monterrey), who I believe had a sister named Gabriela. They are all from here, Monterrey, Mexico. I don't know who Rudolfo Quintanilla is, and have not heard of Esther Quintanilla, but I find it striking that you say they are from Monterrey, as there are not many Quintanillas here in MOnterrey. Perhaps they are linked someway. Maybe this information helps you. Good luck finding out!