Johannesburg - Convicted murderer and Paralympian Oscar Pistorius's grandmother, Gerti, has died earlier at the weekend.Just after 13:00 on Sunday, Pistorius' younger sister Aimee tweeted: "My beautiful & elegant Oumi has passed away. I will love and cherish the moments & memories we've shared x."My beautiful & elegant Oumi has passed away. I will love and cherish the moments & memories we've shared x pic.twitter.com/CHzI7KjF4R— Aimee Joy Pistorius (@AimeePistorius) October 9, 2016The last tweet Aimee had posted before this was on the 92-year-old’s birthday on September 3.Happy birthday my beautiful and loving Oumi.. Love you endlessly x pic.twitter.com/Q4tsmBUbiP— Aimee Joy Pistorius (@AimeePistorius) September 3, 2016Five days before that, it had been Gerti's husband Hendrik's 99th birthday.My Oupi's 99th birthday today!! Such an incredible man who has taught us so much & has always encouraged his family pic.twitter.com/3u5Zytzmdb— Aimee Joy Pistorius (@AimeePistorius) August 29, 2016On his Twitter account, Pistorius's older brother Carl had a picture of himself with Gerti as his profile photo and his biography read: "That's how much you mean to me! That's how much I love you! I'd sell off the whole world to get you back, trade the creation just for you."According to Netwerk24, Gerti died on Saturday. No further details were available on the cause of death, it reported. She had seven children.