"It's an association that not even President Zardari can challenge. A Bhutto addressing an election rally always creates an extra amount of energy among voters, which the party cannot afford to lose with elections round the corner," he said.
The PPP parliamentarian said 22-year-old Bakhtawar does not take much interest in politics and 19-year-old Asifa was too young to address public rallies. Thus, he said, the PPP was left "with no choice but to field Bilawal in active politics."
Bilawal's sisters would make "appearances in the run-up" to the polls.
Media reports have said a group of PPP leaders, including close aides of Zardari and key federal ministers, are currently grooming Bilawal and briefing him on party affairs.
The Dawn reported this group's task had been made easier as over the last year, Bilawal has started taking an interest in politics.
On Thursday, Bilawal was prominently featured on state-run media at the Developing Eight Summit, sitting a short distance from Zardari, though he holds no official position in the government.
A speech delivered by Bilawal on Tuesday to a group of students at a meeting on 'Pakistan: Leaders of Tomorrow' had more thought put into it than was realised by people, the report said. "Do you really think it was just an off-the-cuff speech," said a PPP source.
"It was a 4,000-plus words speech that highlighted every single issue of the country both on the domestic and international level. This series of public interactions to selected students from universities all over the country is the launch of his political life."
During the speech, Bilawal talked about Pakistan's fight against militancy, the PPP-led government's achievements and his willingness to work even with PML-N chief Nawaz Sharif and Pakistan Tehrik-e-Insaf leader Imran Khan.
Another unnamed parliamentarian said familial links have deep roots in Pakistani politics and would stay for a long time to come.
"Can the PML-N contest elections without the Sharif brothers as the party's Premier candidates, or can someone else besides Asfandyar Wali Khan lead the Awami National Party," the PPP leader asked.No defamation campaign against Hina-Bilawal: Pak Army
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Rahul and Bilawal chatted a lot at lunch