Among the descendants of the Sage of Six Paths only the Uchiha clan seems to be alive. Where is the Senju clan (except Tsunade)? Were they eradicated during the wars? Or are they still alive?
It has not been revealed. The list of Senju clan members shown in the series are very few and almost all of them are dead (with the exception of Tsunade):
Here's the list of Senju clan members who are known:
- Butsuma Senju
- Hashirama Senju
- Itama Senju
- Kawarama Senju
- Tobirama Senju
- Tōka Senju
From Senju clan article:
It is unknown if the Senju clan still exists as an independent clan since it neither became one of the four noble clans of Konohagakure nor is there are any known people with the last name "Senju" — with the Fifth Hokage, Tsunade, being the only possible exception. Their legacy however, lives on strongly in the hearts of the people of Konoha.
From Clan Guide article:
Senju (Thousand Arms) of the Forest were one of the founding clans of Konoha. Under Senju Hashirama, they allied with other clans including the Uchiha, to found the Fire Country's ninja village. It is unknown if Senju retains a clan structure in the current Konoha. Tsunade is the only known living descendant of founding clan of Konoha.
Apart from the Senju and Uchiha, the Uzumaki clan also has roots leading to the Sage Of Six Paths.
From Uzumaki clan article:
Descendents from Asura Ōtsutsuki, being originated from the Senju clan,
Therefore, the Uzumaki clan is also one of the surviving descendents of the Sage of Six Paths, along with the Uchiha clan.