The senior BJP leader visited Pakistan on a special invitation from Zen Zia, daughter of Gen Zia ul-Haq, who regards the Indian actor-politician as brother.
Sinha's son Luv accompanied him to Pakistan for the function on Sunday last.
Osman ul-Haq is son of Ijaz-ul-Haq, who is Gen Zia ul-Haq's son and a former Pakistani minister.
Zen Zia ties rakhi to Sinha, who had also travelled to Islamabad on January 18 last year to meet her.
“She is my darling sister and I love her very much,” the Bollywood actor-turned-BJP leader said. “Love and emotional attachment knows no boundary... this is a special relationship of brother-sister between us which is deep rooted unmindful of relationship between the two neighbours,” he added.
Zen Zia inquired about health of Sinha, who underwent a bypass surgery recently. She also expressed happiness over success of his daughter Sonakshi's films, Sinha said.