Complex sentence: O.K.K Sedomon's active political career began in 1962 under UPKO-United National Pasok Momogun Organization, led by himself and his younger brother, G.S Sundang, which represented the native people of Sabah, or North Borneo, as it was known at that time.
Split into simpler sentences: O.K.K Sedomon's active political career began in 1962 under UPKO-United National Pasok Momogun Organization, led by himself and his younger brother, G.S Sundang. UPKO represented the native people of Sabah, or North Borneo, as it was known at that time.