Complex sentence: Sen who was always keen to work with Ashutosh Gowariker and incidentally his father Sameer Sen knew him from before and knowing that Gowariker was looking for someone to compose for his film, Sen asked his father to fix a meeting with him.
Split into simpler sentences: Sen who was always keen to work with Ashutosh Gowariker and incidentally his father Sameer Sen knew him from before. And knowing that Gowariker was looking for someone to compose for his film, Sen asked his father to fix a meeting with him.