I think we might finally get some much needed development for Twilight’s parents in an upcoming episode if Once Upon a Zeppelin’s synopsis is anything to go by.
Meanwhile Rarity’s family other than her and her sister would remain somewhat of a mystery for the forseeable future. It’s almost like they simply don’t want to acknowledge they even exist.
The more I think about it, the more I feel sorry for Rarity’s mom. We really only got to see her once, and there wasn’t anything to really endear her to the fans like some of the others here.