How did Anima get in Zanarkand?

[Ergroilnin]

So I was just reading random stuff about FFX and I wondered about this part of the story.

All high summoners had some guardians and had to fight their way through to show their potential to Yunalesca. But then there is just 10 years old cry baby Seymour and his if I remember correctly dying mother. How the hell did those two get all the way to Yunalesca?

I think it's not mentioned in the game at all but perhaps I forgot about it? If there really isn't any, what are your speculations on the matter?