Kulsoom, 68, wife of former prime minister Nawaz Sharif, breathed her last on Tuesday at a hospital in London after a prolonged illness.
Kulsoom Nawaz-Sharif, who battled cancer for more than a year, died after months of being in a coma, the family said. She was diagnosed with lymphoma previous year, barely a month after Nawaz Sharif was removed from office by the Pakistan Supreme Court, which ordered him to face trial in an anti-corruption court. However, she took interest in politics following the end of Nawaz Sharif's second term as the Prime Minister.
Ms Nawaz was born Kulsoom Rehana Butt in 1950 to a businessman and investor, Mohammad Hafeez Butt, and his wife Razia Begum.
Nawaz Sharif and Maryam were informed about the tragedy by authorities at the Adiala Jail where the two, along with Maryam's husband Captain (r) Muhammad Safdar, are now serving their sentences in the Avenfield illegal assets reference.
Sharif's daughter, Maryam Nawaz, is also in jail.
Kulsoom Nawaz - who became interim president of the PML-N party - made her own political headlines during her detention when she defied her guards and led a procession from her Model Town residence across Lahore city. She contested from the NA-120 seat despite her failing health and secured 59,413 votes to defeat Yasmin Rashid of the Pakistan Tehreek-e-Insaf (PTI).
At that time, he had said that he was leaving behind his ailing wife in Allah's protection and returning to Pakistan regardless of whether he was "taken to prison or gallows". He also directed the Pakistan High Commission in London to assist in the provision of all necessary facilities to the heirs of the deceased.
Begum Kulsoom served as first lady of Pakistan for three non-consecutive terms from 1990-1993, 1997-1999 and 2013-2017.
"Mrs. Kulsoom Nawaz was a courageous woman", Khan was quoted as saying in the statement.
Up until her husband's ouster a year ago, Kulsoom Sharif had never been a politician, but she memorably led protests after the 1999 military coup that ended a previous Sharif administration.
"COAS expresses his grief and heartfelt condolences to the bereaved family on the sad demise of Begum Kulsoom Nawaz".