My guess is that you have UB installed. One of its components is:
Y. Sarevok's Remorse for Yoshimo and Tamoko, by Sovran and Winterine
David Gaider "would have liked to see Sarevok confronted with the idea that not only was he responsible for Tamoko's death (and delve more into that), but Yoshimo's as well". This component sheds some light on the link between Yoshimo, Tamoko, and Sarevok. In SoA, an extra dialogue between Yoshimo and Charname is added, as well as a small extension to Yoshimo's storyline. In ToB, a dialogue between Charname and Sarevok explores presviously unresolved issues such as Tamoko’s *real* cause of death, which can -- and probably will -- also affect the possibility of Sarevok's redemption. [This is also one facet of the upcoming Sarevok Relationship mod.] If you start a new game in ToB but wish to assume you say the SoA part soon, then using the CLUAConsole to SetGlobal("U!SIlmater","GLOBAL",1) is all that's needed. This component requires ToB.