Born in Hyderabad, India, the oldest of six children.
At Osmania University in Hyderabad, he moved between several majors before earning his first degree in science, and his second in journalism. In 1963, he joined the Press Trust of India as a reporter and copy editor. When his father fell ill, he left journalism to look after his family and the company, running it from his father's death in 1965 until it wound-down in 1967.
While still at the Press Trust, he met Roland Michener, then Canada's High Commissioner to India, who had encouraged him to immigrate to Canada. By October 1967, encouraged by friends who spoke well of the country.
In 1978, he joined the Toronto Star, becoming foreign affairs analyst in 1979, news editor in 1982 and national editor in 1985. From 1990 to 1998, Siddiqui was the Star's editorial page editor, and on his departure from that position, he was given the special title of editorial page editor emeritus, a role consulting Star publisher Beland Honderich, and a twice-weekly column, which focused on national and international politics as well as cultural and religious diversity