So you know how Kairi had that 'magic spell' cast on her in BBS that when she was in trouble would lead her to the light of another and that's why she ended up on Destiny Islands? Well, I just had a thought (and if this was explained in some interview or something just correct me) that if that was cast on Kairi and it led her to Sora, then maybe the reason Namine was born in CO is because Ven is there. Maybe the magic led her to the light of Ven since Sora was at that point gone, and she isn't a normal nobody so she wouldn't be born automatically in Twilight Town.

I mean Roxas had a more traditional nobody birth so that explains why he appeared in Twilight Town like all other nobodies. If the magic applied to Kairi, why not her nobody too?

 

IDK, I may be totally wrong here but it makes sense.

Not all Nobodies are born in Twilight Town. They are born in in-between worlds like Twilight Town and Castle Oblivion. Naminé being born in CO might not be a coincidence, but it's not like her place of birth was unusual.

i figured she was born there because she was a unique Nobody/Castle Oblivion exists as an in-between world. 

I always assumed nobodys are born in random places and Xemnas picked them up

The above comments are right. Dusk based worlds, i.e., Twilight Town and Castle Oblivion might be both physically and metaphorically in between worlds. Like the fact that there is a realm of Darkness and a realm of Light, Dusk based worlds must exist in between them and are really hard to get to by other means. It's probably why Sora couldn't access TT for a while in KH II.

Well, that's quite an eye opener that you've put on the table right there! It's not entirely out of the question that the magic Aqua cast on Kairi could have also affected Namine! It would make sense if she was drawn to Ventus in Castle Oblivion, since Ventus's heart is in Sora! Hmm, you might be onto something! It could explain why she was born in Castle Oblivion, specifically!