This is a project that William Wegman did (the guy who photographs the dogs).  He overlapped photos of himself, his father, and his mother.  Most of his work doesn't deal with familial issues, but this set of photographs interested me in relation to my topic.  The merging of a couple and their child.  How united and similar the members of a family can be.  I know that if I did this with my two parents (My grandmother and mother), you wouldn't be able to tell the six frames apart.