The sister of a girl who was allegedly molested and impregnated four times by their father says she wanted to end her pain.

"My dad was doing all this crazy stuff," the 18-year-old told The Associated Press in an interview Thursday. "I got fed up with it until I finally ran my mouth. ... I couldn't see my sister suffer anymore. That's why I wanted her out."

She said her sister, now 19, was 13 when their father started molesting her. The 18-year-old said her sibling confided in her about the abuse after becoming pregnant the first time.

"But I already knew," she said.

The 18-year-old told police in October that her sister was being molested by their father and had given birth to four of his children. The tip led to a search of a rural property in Harrisonville where the family used to live. The property's new owners found two sealed coolers with the remains of two infants on Jan. 1.

Authorities said one of those infants died after not receiving medical treatment for pneumonia. The 47-year-old father has been charged with second-degree murder in the death of that baby, who was born in November 2006.

He also is accused of fathering the other infant whose body was found in the coolers, and investigators said they were looking into the circumstances of that baby's death.

Authorities believe a third baby born in 2004 has been buried in Oklahoma where the family once lived. A fourth child, now a 3-year-old boy, is in state custody.

In addition to the murder charge, the father also was charged with endangering the welfare of a child, statutory rape and two counts each of incest and abandoning a corpse. He was being held in the Cass County jail in lieu of a $500,000 bond.

The suspect's wife, also 47, has been charged with endangering the welfare of a child because authorities claimed she did little to stop her daughter's sexual abuse. She was free on bond and due in court next week for a case review.

The Associated Press is withholding the names of the suspects and other family members to protect the identity of the daughter, an alleged sexual assault victim.

A cousin of the suspect's four daughters said the girls were afraid of their father and that's why none of them sought help sooner.

"He threatened to kill them if they ever said anything," she said Thursday. "They were petrified."

Janeal Matheson, the public defender representing the man, declined to comment when reached by the AP on Thursday. No attorney was listed for the man's wife in court records, and calls to multiple phone numbers for her went unanswered.

A preliminary hearing for the father was scheduled for March 5.