Look this is just bollocks you have made up. Sleep scientists who have actually studied this are clear. The normal range of sleep needed for humans is 6 to 10 hours. Some need 6, some 10.
Whatever amount of sleep leaves you tired and unable to function, and with low empathy (another fun fact is that empathy reduces with tiredness); you have that amount night after night, week after week, month after month, and see how you get on.
Forcing over-tired people to spend time with you, 'for the family' is not going to help you, them or the family. And its cruel. Its like forcing someone with a mobility impairment to go on long walks 'for the family'.
Looking at practical ways to find quality family time together when everyone is able to enjoy it, as OP has very sensibly said she will, is the workable solution.
It sucks to high heaven needing so much sleep. It impairs my life in so many ways. And on top of that, as this thread shows, you also have to put up with the judgey comments of genuinely ignorant people who think you are just wrong about how much sleep you really need, are ridiculous, are selfish, are laughable etc. Do people who talk like this genuinely never stop to think what the implications are for people who need so much sleep? Its hardly a fucking advantage is it? It impacts negatively and holds me back in loads of ways, socially, career options and advancement, being able to learn and do things I enjoy, I could go on. And then there is the fact that people like you shame me for it. Why are earth would I be making it up? Its hardly winning at life to need more sleep than other people, is it? Its a disadvantage not a fucking boon.