I have a rule abt talking pictures of couples: you gotta be married or in a committed relationship. Otherwise, having a portrait done by me seems to be a bad omen for the relationship. More than one couple has returned their portrait to me when the relationship foundered. Neither one of them wanted it and they didn't want to put it in a yard sale either. They figured I wd want it for my archive and they were right.
Couples pretty much do their own thing. They are used to standing beside each other. Or sitting beside each other. Often they assume the sides they have in their bed. They are usually jolly. The occasion is happy: an anniversary. A marriage. The portrait is always for themselves.