IIRC Sotha Sil was the last surviving member of House Sotha. I don't know about Almalexia or Vivec, but I think I read something about how Indoril claimed to have ties with the entire Tribunal. That's what made them the most prominent of the great houses during the time when Morrowind was an independant theocracy.
Vivec can tell you that he himself feels the most kinship with the Redoran, Telvanni are Sotha Sil's favourite, and Almalexia felt the strongest bond with Indoril. He also calls Dres the past of the Dunmer race (pre-Tribunal era) and says that Hlaalu symbolyses the future (post-Tribunal era).