Complex sentence: Her father Manish Ghatak was a well known poet and novelist of the Kallol era, who used the pseudonym Jubanashwa, who happened to be the elder brother of the noted filmmaker Ritwik Ghatak.
Split into simpler sentences: Her father Manish Ghatak was a well known poet and novelist of the Kallol era, who used the pseudonym Jubanashwa. He also happened to be the elder brother of the noted filmmaker Ritwik Ghatak.