Pakistani doctors treating Sarabjit Singh on Sunday said his chances of survival were "slim" as his family arrived in Lahore and visited him at the hospital.
A diplomatic row also seemed to be brewing as Pakistan stopped Indian high commission officials from visiting the Indian convict and New Delhi, in turn, demanded constant consular access.
Late at night, the Indian officials were granted access to the patient.
Earlier in the day, Singh's wife Sukhpreet Kaur, daughters Poonam and Swapandeep and sister Dalbir Kaur crossed over through the Attari border and arrived in Lahore in the afternoon.
A doctor told PTI the family was allowed to see Singh through a window as it was "not good for the patient and attendants to get close to each other".
Doctors briefed the family, telling them Singh was in a deep coma, on life support and in critical condition .
Singh was attacked by at least five inmates in the city's Kot Lakhpat jail on Friday.
He has a fractured skull and cuts on his face and torso from weapons fashioned out of spoons and pieces of tin . His family has demanded that he be sent back to India for treatment.
According to a preliminary report by a senior jail authority, two of the attackers - death row convicts Amer Aftab and Mudassar - have admitted to assaulting Singh with the intention to kill him.
They reportedly said they hated the Indian because he was convicted of killing Pakistanis in a string of bombings in 1990. Singh and his family maintain he is innocent and had crossed over in a drunken state.
In Delhi, external affairs ministry sources said its mission in Islamabad has already sent an official request to Pakistan's foreign ministry for constant consular access.
They also said foreign secretary Ranjan Mathai has issued instructions to provide all possible help to Singh's family during their 15-day stay in Pakistan.
"All of us are extremely concerned about Singh," said union I&B minister Manish Tewari , rejecting the Opposition's charge that the attack was proof of the UPA's foreign policy failure.
BJP president Rajnath Singh demanded that Prime Minister Manmohan Singh take up matters with the government in Islamabad.
Pakistan authorities, on their part, insisted they were doing all they could to help Singh and his family.
An official clarified that Indian officials had been given access to Singh on Friday within hours of his being hospitalised.
"The delay, if any, had been from the Indian high commission side as the vehicle in which the staffers were traveling broke down enroute to Lahore."
With PTI inputs