LOL ... what a politically incorrect thread
Dogs will try to show dominance by humping
It's part of their language
We might find it embarrassing but they take it as a hello - I'm the top dog around here
Now did your dog pick up on a "Change in the order of thing's" when he saw you and your partner? Who knows
But he's trying to assert dominance
You need to assert your own back
Some tricks
When feeding make believe you are taking the first bites then give it to him
When opening a door ... you go thru first
Walking on a leash don't let him pull you ... try to keep him one or two steps behind
That is dog language ... that YOU are top dog