Services will be held at the Leroy Christian Church in Leroy. Their funeral is Friday morning.
Nine-year-old Duncan Connolly and his brother, 7-year-old Jack, were the subject of a national search after Michael Connolly, 40, failed to return them to their mother March 8 after a weekend custody visit.
A 911 call led authorities in rural Putnam County to a remote spot Sunday night where the boys' bodies were found in the back seat of their father's car. Their father's body was found near the car.
Robert Cofoid, Putnam County's appointed death investigator, said Wednesday nothing about how the boys died would be released until "sometime after the service for the boys on Friday."
The Associated Press contributed to this report.