I got this quest too, but my Jeuno fame was only around level 5 or 6 at the time...
If you look up "Mathilde" as a mob on this site you'll see some theories as to what her whole story is. My guess is that she's really "Emelyn" shown in the opening video, and has named her son "Aldo" because the only thing she remembers about her past is her brother (also seen in the video, and most likely the Aldo in Jeuno).
I'm guessing Square-Enix hasn't completed the rest of this story/quest yet, because the boy is nowhere to be found and it just kind of ends there...
Anyways looks like it could prove to be another really interesting quest ^^
Edited, Wed Aug 24 05:17:58 2005