Fuery seems to be younger than Riza, Falman seems to be older than Roy, and Havoc and Breda seem to be the same age (which seem to be around Roy's age range.)
So basically, from what was gathered, I have two ways to go with the ages.
(From youngest to oldest)
1.) Fuery, Riza, Breda, Havoc, Roy, Falman.
2.) Fuery, Breda, Havoc, Falman(?), Roy.
I know for certain that Fuery is the youngest, you can tell that by, well, everything he does. We know Roy's age because of the show/manga. (We also know the Hughes was born the same year though I think he's older.)