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The family of Inkatha Freedom Party MP Mario Oriani-Ambrosini said he had decided to end his long battle" with cancer at the weekend.
Oriani-Ambrosini died at his home in Cape Town in the early hours of Saturday morning at the age of 53.
According to one media report, Oriani-Ambrosini, shot himself.
His family said they respected his decision.
"This choice was made not out of weakness, fear or despair, but from his courage or determination to be the final decision maker concerning his own fate," it said.
"We only love and respect him... more for his bravery in the face of debilitating and ultimately fatal illness."
It said Oriani-Ambrosini said in his last message to the family that he felt he had completed his life cycle.
"He told us: 'I am dying in peace and serenity, surrounded by the love of my family and friends. I am dying at a time when I feel ready. Thank you for your friendship and love which I feel with me at this time'.".
In February, he introduced the Medical Innovation Bill to legalise the use of medical marijuana and pleaded to President Jacob Zuma to introduce laws that gave doctors the power to prescribe alternative treatments.
