Well, I have four girls... so I've never gotten to use a boy name, but have always thought of one 'just in case' (though by this point, it's more of a joke to even THINK about boy names.. lol)...
Hazel wasn't named immediately... it took a bit after she was born to actually settle on Hazel... but of course I had a short list of boy names that I LOVED! Really, really loved them all! They were: Leo, August or Elias. Even now I'm bummed I didn't get to use them (um... but not bummed we have Hazel, if that makes any sense..

)!
For the older three... I think William (we'd call him Will) or Joseph would have been there. ... Michael would have been the middle name (after dh). I always have loved Tobias (Toby) too.
I do love Theodore and Teo as a nickname
