Chances of adopting twin boys?

Since the the odds of someone having identical twins is something like 0.4%, and fraternal twins something like 1%, your chances are pretty low. However, if you're willing to wait for as long as it takes, you can probably eventually do it. Your best bet would be to ask for two boys of similar age, related or unrelated. Unrelated simultaneous adoptions are not permitted in some regions and by some agencies, so that will decrease your chances a bit. But it has been done, and twins do come along once in a while.