Saku and Bo from .hack//GU
they're blonde but their hair are mostly inside hats. the costumes are detailed, may want to think hard before starting on this one. but if you do them well you'll be EPIC!
Hikaru and Kaoru from Ouran High School Host Club
i know other people have suggested them before, but i would like to reinforce their suggestion. i swear it's one of my greatest wish to see actual twins cosplay them, well. and if you're looking for easy costumes, their blazers are available online for purchase, but hand made is always better. our group made 3 of the blazers (we cosplayed ouran right before it was available for purchase) it was legendary. so if you want to make your own but don't think you can handle a very detailed costume, you really only have to make the blazers.
Member of T.H.C.
No, we are not pot smokers... well not all of us...