The family issued a statement to the Limerick Leader newspaper in which they posed a number of questions to McGuinness about his relationship with Kevin Walsh, who was convicted of the manslaughter of Detective McCabe.
The Derry native rejected the claim by the deceased`s family that he met one of the suspects for Detective McCabe’s killing while that person was wanted by Gardaí.
He said: “I did not meet with Kevin Walsh in the aftermath of the killing of Garda McCabe and I have no information about the whereabouts of any other suspects or if indeed there are any other suspects.
“The killing of Garda McCabe was unjustifiable. I have condemned it unreservedly.
“A grave wrong was done to the McCabe family and the IRA have acknowledged that and apologised for it.
“I have never and would never stand over attacks on members of the defence forces or the Gardaí.”
Detective McCabe was shot dead after a bank robbery in Adare, Co Limerick in June 1996.
The McCabe family called on the other six presidential candidates to demand that Mr McGuinness co-operate with Gardaí in its ongoing inquiries as they feel justice for their loss has never fully been served.