Board Thread:Naruto Discussions/@comment-24757127-20140709042852/@comment-25077020-20140709053611

The Senju didn't have any exclusive traits to keep them together. Individuals (other than Hashirama) probably could have had kekkei genkais but there was none that was a clan trait like the sharingan, byakugan, Haku's clan,etc. Nor are they reported to have a Hiden like the Nara, akimichi and some other clans. It's possible that either they split into a few clans and/or were absorbed by other clans due to intermarriage. I personally feel that the former is the likelier scenario b/c it's more reasonable.