If no one has made either relationship exclusive then you aren't doing anything wrong...but are you sure that both men know that you are still playing the field? Its not that you have to tell them who you are seeing, but they should at least know that you are seeing other people, just as they should let you know the same. If they require you to choose between them then of course its your choice, but keep in mind what you really want for yourself first, before you consider what these two want.

hmm.. I could say I been in this situation before, I dated two men and one is older and the other one is younger. actually it give me something to choose from coz both have different attitude and behaviour on how they treated me. I went with my fiance of course whom I could think of myself waking up in the morning beside me and who love me and accept me for who i am. in my case I follow my heart and I could say you can do the same, but its your life and you alone can decide what you want to do with it. good luck

When I first started seeing my last boyfriend, he said that he didn't want a serious, I was also seeing someone else at the same time. It was never a secret and he seemed fine with it at the time. Once he said he wanted to officially be a couple I stopped seeing the other guy. Throughout our 2+ yr. relationship he would bring it up everytime we had a fight.
So if you are in it for fun, that's fine, but if you want one guy to be a serious relationship later, be careful.

The question is, what are you looking for? If you're just having fun, make sure they know it, and enjoy. If you are looking for long-term relationship material, then you need to treat these guys with the kind of respect that you want from them. Guys can get hurt, too.