Complex sentence: Humayun's other brother, Kamran Mirza, had repeatedly sought to have Humayun killed, and when in 1552 he attempted to make a pact with Islam Shah, Sher Shah's successor, he was apprehended by a Gakhar.
Split into simpler sentences: Humayun's other brother, Kamran Mirza, had repeatedly sought to have Humayun killed. In 1552 Kamran Mirza attempted to make a pact with Islam Shah, Sher Shah's successor, but was apprehended by a Gakhar.