Alexander is a perennially popular name (currently in the top 10 for boys) that means "defending men." It's an old school name, dating back to the B.C. era with the conquerer Alexander the Great and a bevy of royals and luminaries. It's also one of my personal favorites (it was on my short list for a son)—I love that you can get a bevy of nicknames from it—Al or Alex, or the currently in vogue Xander.
What do you think of the name? I think it's actually a little more conservative than his girls' choices, but it's a lovely name nonetheless.