Speaking of Eastern beliefs, it is said in chapter 23 of the Tao Te Ching by Lao Tzu:
"Nature is sparing with speech:
A whirlwind doesn't last all morning;
A rain shower doesn't last all day.
What causes these? Heaven and earth.
If heaven and earth can't make something
Furious endure, how could man?"
Surely this is a furious pace! Your only human. Only rabbits, mice and lemmings can maintain that sort of sexual stamina for any legnth of time. That alone has got to become significantly draining after a while. And with all the other things going on in your life!
Sexual attraction really is something of a poor "yardstick" on which to base the health of a relationship. Though many people do. It's true that sex can make or break a relationship, but it should never be the core or top priorty in a healthy relationship; more the icing on the cake, so to speak.
No matter how one looks at it, sex is often the most selfish part of any relationship. Though we may try hard to please our partners, ultimately, if it were not for our own orgasmic gratification, many of use would soon become quite disillusioned with the act.
But good relationships are built on giving in ways in which we have no particular expectations, certainly not that we wish to get anything in return. We give to our partner because we love them, but we love them because we truly want them to be happy, not because they are necessarily inherently "pleasing" at any given time. No relationship is perfect, and many bumps in the road can be expected.
Though, without other forms of recreation, and solid verbal and decidedly non-sexual -- though not necessarily non-intimate -- forms of communication, any relationship is assuredly doomed with time.
I was in a similar situation years ago, with a woman I dated off and on for two years. She was a basic work-a-holic, working up to 80 hours a week as the director of a chain of houses for the mentally retarded. Our first date was fabulous, we went out for a day in the city -- ate, shopped, had a fantastic time. Never again did she find the time for such.
Our typical dates for the next two years consisted of getting together at 11:00 at night, eating in an all-night restaurant, closing out the local pool hall, and then retiring to bed. She never wanted to talk about anything, she only wanted to be sexually intimate. Suffice to say, I never grew so tired of sex. Eventually she began to correspond with other men, and the relationship ended when she showed up at the door of my oldest friend alone -- someone she had only met but one time, though had tellingly been more than a bit forward with.
Basically, you need some time to yourselves if you want to have any chance of saving things. You need time to pursue your own interests, and go out from time to time with friends alone. Your time apart will make your time together all that much more special. And remember that sex is not always the ultimate, or most nurturing way to express your love. Though it does have its place in any good relationship, so do cooking meals, watching a movie together, holding hands on a long walk, or suprising her with small, unexpected gifts.
Perhaps this is a good opportunity to lend some support to both your brother and parents. But don't allow it to come between your relationship completely. In a sense, it sounds like he's making his own bed. You have a right to be happy. Perhaps you can find something more of a balance between these seemingly conflicting priorities though.
I wish you luck. I do hope everything works out for the best for everyone. Take care.