"As you can imagine our entire family is devastated, we are in a state of total shock — firstly about the tragic death of Reeva who we had all got to know well and care for deeply over the last few months," Oscar's uncle Arnold Pistorius said in Pretoria.
"We are all grieving for Reeva, her family and her friends."
He said the family had seen first hand how close Steenkamp had become with Pistorius during their time together.
"They had plans together and Oscar was happier in his private life than he had been for a long time."
Arnold said Oscar was "numb with shock as well as grief".
"Obviously… we, as a family, are also battling to come to terms with Oscar being charged with murder," he said.
"Words cannot adequately describe our feelings. The lives of our entire family have been turned upside down forever by this unimaginable human tragedy and Reeva's family have suffered a terrible loss.
"As a family we are trying to be strong and supportive to Oscar as any close family would be in these dreadful circumstances."
Pistorius was arrested on Thursday after Steenkamp, a model, law graduate, and participant in the Tropika Island of Treasure television show, was shot dead in his home.
He was charged with murder at the Pretoria Magistrate's Court on Friday.
Pistorius remained in custody at the Brooklyn police station and was expected to make a formal bail application on Tuesday. – Sapa