Richard McCann, 45, says he has contacted police in relation to a malicious comment on Facebook, which he received after posting a status in tribute to his mother.
Wilma McCann was 28 years old when she was attacked and murdered by Peter Sutcliffe on October 30, 1975.
Speaking to The Yorkshire Post, Mr McCann said: “It is shocking. I’ve found the anniversary quite emotional. I had to pull my car over yesterday and cried on the side of the motorway. The true severity of what took place and what I had lost sunk in. It’s not just a story I read about in the papers – this is my mum. So to get that comment after feeling quite emotional...I was angry.”
Sutcliffe had been driving through Leeds in his green Ford Capri when he saw Ms McCann thumbing for a lift.
After parking near the Prince Phillip Playing Fields, close to her home, he attacked her with a hammer and fled the scene.
Sutcliffe went on to murder 12 more women and at least seven more were left for dead before he was finally arrested – five long years later.
Her brother Richard also led a troubled life and served time in prison on drugs charges before turning his life around.
He is now a father-of-three, motivational speaker, and author of two best-selling books about his life – Just A Boy and The Boy Grows Up.
Former Bradford lorry driver Sutcliffe, now aged 69, remains in custody in Broadmoor and is unlikely ever to be released.