Bilawal - A profile
Bhutto, who narrowly escaped an assassination bid on October 18 in Karachi, in her will named her husband Asif Ali Zardari to lead the party, but he gave the responsibility to his son, a party official said.
Bilawal, the eldest of Bhutto's children, is described as a fitness freak and a keen sports enthusiast. He is a black belt in Taekwondo and also loves swimming, horse riding, squash and target shooting.
In a rare interview to a Pakistani daily three years ago, he said he regretted that he could not play cricket because of the "circumstances in which my family had been put".
Bilawal spent his childhood with his two sisters Bakhtawar, 17, and Asifa, 14, in Dubai and London after his mother went into self-imposed exile.
He did his 'O' levels from the elitist Rashid School for Boys in Dubai and served as a vice-president of the students' council there. He joined Oxford soon after turning 19.
Asked about joining politics when he was 15, Bilawal said, "We will see, I don't know. I would like to help the people of Pakistan, so I will decide when I finish my studies.
"I can either enter politics, or I can enter another career that would benefit the people," he said.
Bhutto fiercely guarded her children's privacy and kept them away from the prying eyes of the media.
But like his mother, whom he doted on, Bilawal has spoken about Pakistan's problems which he said could be solved if there democracy in the country.
"I think there wouldn't be such a problem if a dictator doesn't come and take over after every couple of years. That contributes to backwardness and poverty. Democracy is the only way out. The founder of Pakistan believed in democracy. He did not believe in dictatorship, and Pakistan was not founded for that. So there shouldn't be a dictator," Bilawal aid. "About the justice system, I don't know how well it is working over here, but my father has been in prison for eight years and has not been charged with anything, nor has anything been proved," he told a local daily three years ago.
Bilawal also passionately spoke about the "cooked up cases" against his father Asif Ali Zardari, who spent eight years in jail.
"He (Zardari) is the only politician in Pakistan who has been kept behind bars for eight years. It is not only a crime against him, it is a crime against me and my family, who have been robbed of our father's company and guidance when we needed him," Bilawal said when he came to meet his father after a four year gap.
Asked whether he would like his father to be free through a deal with the government or would you like him to be exonerated by the courts, Bilawal's response was: "He should come out with honour. If there is a deal going on, then why a deal after all the fake cases?" Bilawal also spoke about his two younger sisters. "My middle sister (Bakhtawar) doesn't talk about it (about Zardari being in jail) a lot but my younger sister (Asifa) asks me and I tell her that we have to be strong and one day he will be free and will be with us." Zardari was released in November 2004 after spending eight years behind bars.
On his mother, Bilawal said, "She tries to find time for us whenever she can. I think she is doing a good job as a mother, even though being very busy."