There is no normal here... Some folks/kids are just "funnier" than others, or so they think they are. Some are more rebellious, sensitive, rude, sweet, etc. So it sounds like you have a challenge on your hands...
You could implement a better punishment than a timeout. If they are double-teaming, then first off I would punish all for the sins of one to keep them from egging one another on. Tell them that this will be the case from now on and stick to it, no matter what. It turns one of them into a hall monitor very quickly.
Then explain just ONCE either today/tonite that also from now on, they are old enough to know right and wrong*. Trust me, they do, that's why they're smirking. And that since they know, there will be punishment X whenever they Y, Z, etc... (list all they have done that you can think of). Then pick something they both like, dearly, and take it away as punishment X.
With my, very spirited, daughter, I take away her blanket. So "blanket goes in time-out" Usually for 5-10 minutes (she's 4), but if she teases the cats or dogs, it goes away for the rest of the day and she doesn't get it back until the next day.
*I noticed over a year ago (she was barely 3!!!) that when she would come out of time out, and I asked why she was in there, she knew why without me having to say it. So she KNOWS what she has done. EVEN NEW THINGS. I do give a one sentence why not, (i.e. that hurts people) but that is it no more discussion. Then she must make amends with the one she offended, man or animal... and we move on.
Good Luck!