So are the Sohmas all blood related?

Some years back, my friend and I (who read and watch the story), talked about this. I think we gathered they were cousins but I'm not sure where we got that info. I haven't actually sat down and watched the whole show without doing something at the same time since I saw it many years back. I can't remember but in a foggy distant memory, if I recall correctly, wasn't Kagura introduced as a cousin of the Sohmas?

I don't know. Lately I do two or three things at the same time that I haven't actually paid 100% attention to anything I watch.