Don't do it much any more, but when I called dances I never really did solve the triple-couple partner problem. It happens when a couple try to include the baby-in-arms or toddler in a set dance. Have you ever tried to strip the willow with a baby-in-tandem partner?
I've tried putting them all in their own sets, with limited success. I've tried gentle tact, organized all children sets. Usually it does sort itself out by the end of the night, it's tiring lugging a child around while you dance, but it's a real problem. Joy