Manya

Manya Vargas is the wife of Nathan. She and Nathan own a house in Megaton and live there. If you ask anybody for the word around town, they will direct you to Manya. Manya's dialogue changes over time, so keep going back to her to learn more. If Nathan dies, she will comment on "how quiet it is now that Nathan is gone", and you will not be able to interact with her furthermore.

Characteristics
Manya is one of the oldest residents of Megaton, and as such knows much about the history of the town. If you ask her about Megaton and how it was built, she will tell you stories about how the town started.

She is also a member of The Railroad. You can find this out by finding a holotape recording she keeps in her home and she admits to it when you ask her about it while you are on The Replicated Man quest.