I think there is more than Sidney on Regina’s side? Dr. Whale called her about David in Snow Falls, eps 3.
Obviously that nurse in the psych ward at the end of Skin Deep is with her.
At this point I would put MM on Emma and Henry’s side.
I think Rumps/Mr. Gold is his own side. I don’t think he is on Emma’s. I think he is on whoever suits him best side and affords him the advantage. Remember how he told Regina in The Thing you Love Most how she should have come to him regarding Emma. He wasn’t on Emma’s side there. He is on Mr. Gold’s side:)
Not sure where I would put Archie or Leroy at this point. We will see about Ruby.