I had originally tagged post #1252302 as heart_hands_duo, but I took it out when I realized it didn't necessarily fit in with the rest as they're not making the heart shape with their fingers but rather using the entire length of their arms. Tried to see if I could find some other examples and came up with these:
post #1167511 (Maybe? In any case, this is the only one that should have the heart_hands_duo tag too)
heart_arms_duo would seem to be be most sensible name for it. I thought of just heart_arms too but it could warrant being a separate tag for a single person forming a heart with their arms. I haven't been successful in finding a clear example yet, though.
Updated by anon153