lol, I know what you mean it is kind of weird .... but you know what is even weirder, my great great great gandparents were brother and sister and didn't even know it :/
Well in-laws are typically not blood related, where as cousins of any type are....I think...I only find it weird when your 2nd cousin is also your grandpa or something like that.
Its not always the case some people call them aunty or uncle but its usually your own cousin's children that are your second cousin's. I'm not sure so dont quote me on it!!