Campbell Bridges died in August 2009 after being attacked in the grounds of his home near the southern town of Voi. Eight men have gone on trial accused of killing the 71-year-old geologist during the ambush.
Bruce Bridges told how he often saw the accused men in a pick-up truck belonging to education minister Calist Mwatela.
He also revealed another vehicle used to block a road at their home was registered to the MP's wife.
Mr Bridges identified the eight in the dock by name and said he had known them since they encroached on to the family ranch.
He told the court in Mombassa: "I know all of them both physically and by name."
The trial heard how two security officers who protected the Bridges family were abducted shortly before the ambush.
John Nyamu and Peter Nyalu were snatched, handcuffed and beaten while on patrol in July 2009.
Mr Bridges, 33, recalled: "The accused told them they would kill my father and set the whole camp on fire."
Campbell was driving his pick-up truck when he was ambushed by a gang of up to 30 armed men. He fought off the mob with his son and four Kenyan staff but later died of his injuries.
The family said the attack was connected to a dispute over control of his gemstone mines. It has emerged Mr Mwatela is the majority shareholder in the company that was in dispute with the Bridges.
Mr Bridges told how they had begged for police protection just hours before his father was killed. As they spoke to the police chief, a second MP rang regarding the row.
Mr Bridges said: "He showed us his last call registry that showed gender minister Naomi Shaban had called him."
It has been alleged that Ms Shaban produced her payslip to have her relative – who is charged with the killing – released on bond. The Bridges family has accused Ms Shaban and Mr Mwatela of interfering with the investigation. The trial continues.