When I lived in Cheltenham, there was a couple who I saw a few times, who had two tandems, both with kiddy cranks, and I very occasionally saw both of them with kids on the back, but more often one of them, who I assume had just dumped a kid at school before going to work.
There's a woman I've seen a few times around Queenstown Road in Battersea, who seems to be doing much the same.