murdered in December 2007 and he had the chairmanship of her Pakistan People's Party (PPP) thrust upon him.
After maintaining a relatively low profile for several years, Bilawal launched his political career with an impassioned speech at the family mausoleum in southern Sindh province on the fifth anniversary of her death.
"Bhutto is an emotion, a love," he told a crowd of more than 200,000 supporters of the party founded by his grandfather Zulfikar Ali Bhutto, the charismatic premier deposed and hanged by military dictator Zia-ul-Haq in 1979.
"Every challenge is soaked in blood, but you will be the loser. How ever many Bhuttos you kill, more Bhuttos will emerge from every house."
Though Bilawal will not be old enough to run for parliament until September, his face adorns PPP election posters and TV adverts, framed between Zulfikar and Benazir, who was killed in a gun and suicide attack.
The PPP endlessly eulogises the dead Bhuttos as "martyrs" to the common man's struggle against oppression, but the threat of a Taliban attack means Bilawal has barely been seen in public in the run-up to the May 11 vote.
His only significant appearance so far came with his father, President Asif Ali Zardari, in a bizarre middle-of-the-night gathering on April 4 that was originally billed as a major rally to kickstart the PPP campaign for re-election.
A handout picture released on April 4, 2009, shows Bilawal Bhutto Zardari, chairman of the ruling Pakistan People's Party (PPP) flanked by Pakistan's President Asif Ali Zardari, and former PM Yousuf Raza Gilani as he speaks on the 30th death anniversary of Zulfiqar Ali Bhutto, in Naudero near Larkana. (AFP)
Bilawal appeared uncomfortable as he addressed the small crowd haltingly in heavily accented Urdu, a far cry from the practised polish of his December speech and evidence of his upbringing in exile in England and Dubai.
Perhaps more damningly for the leader of a centre-left party, some PPP faithful have been unimpressed with Bilawal's failure to meet and charm the ordinary voter -- something that came naturally to his mother and grandfather.
Given the rise over the past two years of cricket legend Imran Khan's Pakistan Tehreek-e-Insaaf (PTI) party, with its energetic youth wing, Bilawal's age is an asset for the PPP as it seeks to appeal to 25 million voters aged under 30.
The freshness represented by Bilawal is also important in light of the corruption scandals that have plagued Zardari -- nicknamed "Mr Ten Percent" -- and indeed Benazir, whose two governments were thrown out over graft allegations.
In her autobiography Benazir said Bilawal's birth was met with celebratory gunfire outside her hospital and cries of "Jiye Bhutto" -- long live Bhutto.
With no other obvious leader emerging in the PPP, the young man whose name means "one without equal" looks likely to carry on the political legacy bequeathed to him by his mother and grandfather -- whether he wants to or not.