Stuart King, brother of the twins' mother Macsyna King, has begun giving evidence in Auckland District Court at the coronial inquest into the 2006 deaths of the Chris and Cru Kahui, who died in hospital from severe head injuries .
Mr King said he spoke with Mr Kahui, the twins' father, about handing himself in to police.
Mr Kahui had wanted to hand himself in to police but he said he had never hurt his three-month-old twin sons. Mr King said.
Mr King said he told Mr Kahui he should only hand himself in if "he'd done it", and it would not help matters if he had not.
Mr Kahui was found not guilty of their murders in a High Court trial in 2008, at which his lawyers said Ms King killed them.
The twins' mother has denied she caused the injuries which led to the babies' deaths.
