Or 20, depends on what source you use. They could well be 20 if GL wants them to be. Their ages are never specified in the movies, so there's no final on that. I guess they're 20.
And I don't see the problem with a "hole" if we don't get to see Padme die. If she doesn't die BEFORE ANH, she definately dies IN ANH when Alderaan blows up. The final explanation what happened to Padme comes in ROTJ.... I mean, what's the problem. Her death is irrelevant in the OT anyway.
luke and leia had to be 1 in ANH, because luke started training at 18, and he started training in ANH, so that would be logical...and my dad who knos evrything, literally evrything about SW said that padm? most likly dies in ep.III, and hes rarely wrong bout nething, lets just hope hes wrong about this...