Dewastich, the Zoroastrian ruler of Sogdiana died fighting the Arabs and became a symbol of resistance. But, his descendants were captured & converted, and they went on to become one of the most prominent aristocratic family in the Islamic world, serving Seljuqs, Ghaznavids, etc.

Muhammad ibn Suri, the Buddhist ruler of Ghor, overcome with shame after his capture by the Ghaznavids, consumed poison. His son was converted and placed on throne. Some times later, the Ghorids would hunt down the latter till Lahore while furthering IsIamic conquests in India.

Iran after the Arab conquest is filled with such cases. Sasanian nobles, Parthian families somehow making peace with their new reality, tracing their genealogies to Abraham, giving new meanings to the ruins of the House of Sasan.

Though the main line of Shahis escaped to Kangra, I wonder did any similar case happen there as well. Ancestors fought Arabs, himself froze to death in Peshawar while fighting Turks, but sons converted & few cent. later they showed up at Kannauj carrying the banner of Holy War.

Powerful families or institutions never really die out. They just perpetuate themselves under new names, different beliefs.