Heaven help us all, but I agree with JR
If it's just a case of unintentionally being tangled up, then I have nothing. If it becomes clear that A1 is trying to keep B1 pinned behind him/her, then it's a hold on A1. If B1 is using the pinned arm to pull A1's arm off the ball, then it's a hold on B1. I don't see these as fouls very often. Usually, one or both players realizes the play is over and tries to get untangled. Detangled? Disentangled? Dis-tangled? Dat-tangled?
Chuck