Complex sentence: It opens with two young men, Aaromal's son and his nephew, the son of Unniarcha (Aaromal's sister), learning how Chandu's treachery resulted in Aaromal's death.
Split into simpler sentences: It opens with two young men, Aaromal's son and his nephew, the son of Unniarcha, his sister. They were learning how Chandu's treachery resulted in Aaromal's death.