Yes, I stand corrected. I have been wrong on multiple counts and confused his behaviour with that of Dharmendra, who I believe converted to Islam to marry Hema Malini.
For a long time a story was doing the rounds that Kamal Haasan was named so by his father to honour his friend Yakob Haasan whom he met while in prison during the freedom struggle. That turned out wrong too, and Kamal Haasan later called it BS. His name is derived from Kamal (Lotus) and Haasya (Laughter).
Damn, the amount of misinformation that becomes mainstream is incredible.