When Brooklyn returned to Manhattan with Katana, Nashville, and Fu-Dog in 1997, Tachi was still an unhatched egg, nicknamed Egwardo by Brooklyn.  The egg was placed in the rookery below Castle Wyvern and often guarded by the clan's beasts: Bronx and Fu-Dog. ("Phoenix", "Idyll or Nightmare")
Since Tachi will be the only member of her rookery generation, it is somewhat likely she will be aware of her biological parentage (Brooklyn and Katana). 
Almost nothing is known about Tachi's physical features, though one can speculate that she will combine features of both of her parents.