Oyakodon isn't super rare (although I wish there were more) but it's been a long time (if ever) since I've seen one where the mother is holding and comforting the daughter during her first time. Also in similar scenarios where the older/experienced one is an aunt/sister/senpai etc. Bonus if the experienced one fucks the guy first to make sure he's good enough and is also getting off on getting the younger one bred.
(Small Restaurant Sai from Amakuchi Virgin by Makinosaka Shinichi, closest I could think of)