http://www.chronocompendium.com/Term/Orlha.htmlhttp://www.chronocompendium.com/Term/Orlha_(Relation_to_Tia).htmlWell, I know there were topics about this. It seems the encyclopedia tends to think an unknown tragedy separated them or they are dimensional equivalents of each other.
So let's see the script once again:
Orlha:
According to old legends,
'"Twins are signs of tragedy..."'
When I was a child, I was
separated from my mother and
sister, who left El Nido...
I only had my father.
I felt as if half of my
body had been lost.
There was a huge
void in my heart...
So according to the El Nido culture, twins are misforturne. So their mother had to take away one of the child and left their home town. The game doesn't give enough details, but "left El Nido" kinda hints they went to the mainland, and the Ultimania confirmed that they moved to the mainland. But no matter what, they lost contact with each other since then. Before the separation, each of the twins kept half of a Blue Brooch, hoping they could meet again someday.
Orlha had been living with her father before moved to Guldove, we don't know when did that happened, but 10 years ago seems to be a popular time.
Tia probably lived with her mother in the mainland, maybe she knew Doc. Later Tia and Doc moved to Guldove from the mainland for some reason....
So maybe Tia died in Another World while Orlha met the similar fate in Home World. The 2 survivors from different worlds united at last, like Dario and Riddel.