Complex sentence: He also mentioned, as an old motivational factor from his childhood, the apprehension of his parents Md Manjur Hossain and Mrs Rezia Begum's impending death ultimately compelled him to learn and theorize how to adjust to the phenomenon of death.
Split into simpler sentences: He also mentioned of a motivational factor starting from his early childhood as the anticipatory apprehension of his parents-Md Manjur Hossain and Mrs Rezia Begum's death in unknown future. It ultimately compelled him to learn and theorize how to adjust to the phenomenon of death.