It wasn't very long, but in my dream my family was still going to the Mormon church (exmormon IRL) and there were only two other families that went to our ward and we were the only ward. Secretly I was visiting this site and then I figured out my sister was on here trying to get out of the church too. Could this have some sort of deeper meaning?

It sounds like you dreamed what we all hope for, That our family will see through the facade.

+1 is your sister the one that you wish you were closest to? Or are you already close? That's probably why you "chose" her instead of it being another family member. I have similar dreams about my brother.

That's for sure fidget!

Actually my sister and I had a lot of trouble getting along when we were younger. Now we get along better with maturity and even though we have a good relationship, it's still not the best.

I find it interesting though because my family is not Mormon anymore. There is actually a different family I currently wish would leave the church very much so. Perhaps my mind replaced them with my family.

It's definite possibility. Or minds like to stay with the familiar.