Right of son of a pre deceased daughter in the property of grandfather

Religion : Hindu One of our senior colleague "Mr. X" had one son and one daughter. The daughter died when he was still alive, leaving behind a son which was abandoned by her husband and brought up by the maternal grand father i.e. our colleague Mr X. Over a period Mr X, his wife and his only son have died.Only surviving members now are his daughter-in-law,her one son and pre- deceased daughter's son. Mr X has left behind a self acquired flat in a housing Society in Delhi, which still remains in his own name,though he died more than 10 years back. Can the daughter-in-law and daughter's son, both can claim a share in this property ? If yes, in which proportion? There is no other claimant.Also kindly advise way forward.I am only enquiring with the aim to rehabilitate the destitute grand son of Mr. X who has been turned out of the flat and is living on roads. Thanks and regards,