It still doesn't make any [censored] sense.
You do realize that Bittercup, who claims to have been the 'girlfriend' of half of the kids who came from Lamplight, is probably no more than 17 or 18 years old at -most-, right?
You're not really so naive as to think, for a second, that she is either an isolated case... or not romping around in the hay with all those 'boyfriends' of hers, right?
You do realize that YOUR character is only about 19, yes?
The fact of the matter is... despite Fallout 3's world having no mechanics for it... "Kids" grow up. They've been living in that hole for almost 200 years. That means SOME of them are going to breed... and obviously, since there are still kids there, they have been. Furthermore, kids who grew up in lamplight and had kids of their own are probably very likely to bring their children BACK to Lamplight, in the event they cannot take care of them.
It's not at all impossible. It's not even far-fetched.
Them not getting completely annihilated by raiders, slavers, and each other was perhaps a bit far fetched... but no more so than any -other- group of survivors in any story ever told.
As for Megaton... well... Megaton has been explained three different times in almost the exact same way... by people who have never really had much contact with one another whatsoever. Something tells me that it makes perfect sense to anyone who actually paid any attention to the story.
I begin to think you're just complaining to complain... and that's the worst kind of complaint there is, because it doesn't even require any kind of thought or logic. You can just sit there and say 'It doesn't [censored] make sense' all day long, and never justify your case. If that's not the case, then hopefully you better understand now the points for why places like Megaton and Little Lamplight exist. There have been many perfectly understandable explanations given.
Otherwise, well... I see no further point in arguing it.
I would much rather see more people come and point out reasons why Rockstar should -not- make a Fallout game...
... that would be fun. I like hearing legitimate complaints.