In the games
Black and White
Anthea and Concordia are first seen in the opening sequence of Black and White. The player only encounters them in N's Castle, where Anthea heals the player's Pokémon, while Concordia tells the player more about N's past and Ghetsis.
Black 2 and White 2
Anthea and Concordia are seen in the original Team Plasma's safehouse in Driftveil City. They give the player more backstory about themselves and N, revealing that all three of them were orphans that Ghetsis took in. They were then put in charge of caring for N while he was a child.