Your family should be the ones that understand you and support you more than anyone else in the world. It would seem like an evolutionary instinct to protect your own blood. Unfortunately most of the people I know have strained, distant or just plain ambivilant relationships with their families and it's usually because someone is placing their ideals above people.
While convictions are respectable amd important, I find it a shame that my sister would not attend our brother's wedding because he was marrying a woman who had been divorced. My mother informed me about a month ago that she would not accept anyone I might be in a relationship with since I didn't have a biblical reason to get divorced. Then my brother who has always been the quiet rebel (though never as extreme as me) said he couldn't support me but that he wouldn't oppose me either. It saddened me today that one day when I buy an engagement ring I have very few people who will give a shit.
This past year has changed my mother a lot and so I still talk to her but when she asked if I was coming to visit any time soon I had to be honest. "I don't really have any friends to see up there and it will only take one day to see Grandma and the other relatives. You don't agree with much of what I do so what's the point?" I said it as kindly as possible but extremely honestly because why lie?
I don't know why people let their families treat them poorly these days. This isn't the hunter / gatherer age and most of us don’t live in tribal regions of the world where our families are integral to our survival. One of the many things I love about my job is that I get to meet and spend copious amounts of time with some great people who have become more of a family to me than any of my biological family. There are some great people in the world, some shitty ones too (most likely your family) and nothing is stopping you from making your own life and family. Cut the poison out of your life and do not feel guilty. Blood is thicker than water but sometimes that thickness is like a pit of quagmire dragging you down. As always, I recommend a little bit of alcohol....to thin the blood out of course. If you love something, you don't hold it tightly - you celebrate it and set it free.