Super Hero Costumes, Sharing Christmas Gifts?

3 gifts
Iron Man goes to your youngest.
Hulk to the oldest.
The other two wrapped together with both boys' names on them.

They will share them all anyway, right? My kids have pretty much always been expected to share with their toys, even when it "belongs" to them exclusively. It has never been a problem. And since that is the expectation your boys have always had regarding costumes, it shouldn't be an issue with them either.

ETA:
We do this all the time. In fact, I just finished wrapping an old fashioned popcorn popper and put both the kids' names on it. They will love it. Any video games (not handhelds, but like PS3, Wii, etc) all those things are family or joint gifts. And usually there is an actual game of some sort (board games or whatever) and those are joint or family gifts. I grew up with stuff like this. I didn't know other people didn't. hmmm learn something new every day. :)

I have had gifts that were for both my boys and just have them open it together.

Boys that age, the costumes would be a different size.
It that right?
Also, kids that age, will not want to share, or share ALL the time, their costumes.

I dunno. I would give each boy, the costume they really had hoped for.
Did you get the Hulk and Iron Man costumes?
So, I would give each of them the one they wanted/wished for.
Then as you said, the 2nd costume they get is one of the others you got.

I gave my kids joint gifts all the time, board games, boxes of dress up stuff, play sets (trains, building sets, art stuff, etc.) Just put both their names on the tag. I think it's GOOD for them, it encourages sharing and playing together, which my kids did, a LOT!

We do this all the time and just call it family gifts. In your case since it is just for kids, just put both of the names on it.