No issues being an atheist in my family. My brother's a bit of an anti-religionist, my father's a... well I don't know. Very informed, I guess. Studied to be a minister, but that was the United Church of Canada where believing in the fairy tale stuff is not required. My mother stopped taking us to church after we went on a canoe trip in the wilderness and she decided she felt closer to God there than she ever had in church.
So, I suppose it's a family of independent thinkers more than anything else, and everybody's got their own personal beliefs. So I don't have problems unless they get the impression I believe in something weird.
Actually, come to think of it, there are some stumbling blocks with respect to my being a bit of an apophatic mystic, because I don't believe in anything, including disbelief, and they find that confusing. For my brother in particular, you have to pick belief or disbelief. I pick neither belief nor disbelief. I just like a good narrative.
Around here, it's actually hard to tell who's religious and who isn't. It's not something that comes up. My best friend and her husband are Pentecostal, and I'd have expected them to be banging on about it all the time from what I know of that denomination, but it's never come up at all. They don't even say grace. Not when I'm there anyway.