I use Gimp at work, but I'm more of a photoshop person.

Picasa often sees familial connections with its face recognition - my grandkids are often suggested for one another particularly the younger ones.

At work, where I also use picasa, it has even picked up the faces in the photographs on the wall, behind the actual subjects of the photograph. I guess given enough instances of this recursion we could have a pretty good optical illusion going :-)

Anyway, sing out if there's anything gimpy I can help with :-)