Ménage à trois?

Goodly choice again today, but this must take the (dog) biscuit.

What, actually, caught my eye was the strange posture of the wee wiry one. Then I spotted matey-boy's leg, re-adjusted the angle and shot again.

I think we've just about covered all possibilities from a Ménage à trois, through the idea that Joe was the dog, Joe was their 1st/only son, etc.

Suggestions in a plain brown envelope please.