Honolulu — The father of a Hawaii boy who went missing 20 years ago pleaded guilty to manslaughter on Wednesday in a deal with prosecutors that requires him to reveal the location of the child's body.Peter Kema snr also entered a guilty plea to hindering prosecution and agreed to a 20-year prison sentence, with a mandatory minimum of six years and eight months if he helps authorities find the remains of his son, Peter jnr, who was 6 when he disappeared.If Kema doesn't cooperate, prosecutors can ask for a 25-year term, Hawaii County Deputy Prosecuting Attorney Ricky Damerville said."This saga doesn't end until we find that body," the prosecutor said after the hearing on the Big Island.Peter Kema didn't provide those details in court on Wednesday. He only responded "yes" when a judge asked if he recklessly caused the boy's death by not getting him medical treatment.In the late 1990s and early 2000s, the boy known as "Peter Boy," became the face of a campaign for missing and abused children. Posters and bumper stickers asked, "So where's Peter?"Kema and his wife, Jaylin, have long been suspects in the boy's disappearance, but prosecutors said they didn't have enough evidence to charge them until last year, when a grand jury indicted the couple on murder charges.Jaylin Kema pleaded guilty last year to manslaughter in the first official confirmation that the child was dead.In exchange for a one-year sentence with credit for time served, she agreed to waive her marital privilege and testify against her husband if he went to trial.She agreed to facts prosecutors laid out in court about abuse suffered by the boy, her failure to get him medical treatment and his eventual death.'Where is Peter Boy?'In 1996 and 1997, extended family members, most of them now dead, were concerned that the boy's father was abusing him.An arm injury was left untreated, festering and filling with puss until there was a hole so deep someone could put a finger inside it, Damerville said last year.Despite having health insurance, Jaylin Kema didn't get her son medical treatment and didn't report the abuse because she was afraid of her husband, Damerville said.Sometime between May and June 1997, the couple's then 4-year-old daughter heard Jaylin Kema calling out for her husband and saw her trying to resuscitate the boy. The girl later saw her brother in a box, Damerville said.Prosecutors believe the boy died from septic shock from not getting medical care. They do not believe Jaylin Kema knows the location of the body.Peter Kema told authorities that he took his son from the Big Island to Oahu and gave him to someone named "Aunty Rose Makuakane" in an informal adoption. Police could not find a woman as described by Kema or airline records that indicated he had flown there.Four years ago, Hawaii County Prosecuting Attorney Mitch Roth vowed to give the cold case a fresh look. Roth said he knew that without a body, prosecuting the couple would be difficult.A turning point came when Kema's wife agreed to testify against him, Roth said.Roth was in court on Wednesday sitting next to Peter Boy's maternal grandfather."Now we'll know the truth," Roth said. "It answers the question for the public: Where is Peter Boy?"