A couple belonging to a cult-like Christian church brutally beat their older son to death during a “counseling session” over his desire to split from the insular fold, authorities said Friday.

Congregants at the Word of Life Christian Church in New Hartford said the session was called Sunday because Lucas Leonard, 19, wanted to move on with his life, according to Police Chief Michael Inserra.

“We still have not concluded why the session turned so violent,” Inserra said before a court hearing for Bruce Leonard, 65, and Deborah Leonard, 59, who are charged with manslaughter.

Lucas was killed and his 17-year-old brother, Christopher, was seriously injured when they were punched, kicked and whipped with computer cords over 10 hours. The brutal counseling session lasted from about 9 p.m. Sunday to 7 a.m. Monday, according to Oneida County District Attorney Scott McNamara.

Their sister, Sarah Ferguson, 33, and three other people are charged with assault. Also charged are Joseph Irwin, 26, of Chadwicks; and David Morey, 26, and Linda Morey, 54, both of Utica.

The parents appeared in court Friday for a hearing on whether there was enough evidence for the case to move forward. During the hearing, church member Daniel Irwin said he saw a bleeding Lucas rolling on the floor after his dad struck him with what appeared to be a belt.

Deborah Leonard gazed down, her long, graying hair hanging in front of her face, as a cop testified about photographs he took of Lucas’ battered body. She didn’t anticipate how vicious the “intervention” would become and didn’t “have the mental toughness to stand up and say, ‘Wait a minute — this is going too far,’ ” said her lawyer, Devin Garramone.

Bruce Leonard’s lawyer, Donald Gerace, said what happened was a family matter not connected to the church — and that the couple had no intention of seriously injuring their sons.

“There is absolutely no evidence to corroborate that allegation. None,” McNamara told the Utica Observer-Dispatch. “What I’m most concerned with is that I have a 17-year-old victim who is laying in the hospital and is it right, fair or appropriate for (any media outlet) to say he’s a child molester when there’s no proof of that?”

Several children were removed from the church and handed over to the Oneida County Child Protective Services, according to reports.

Meanwhile, police sought to dispel rumors that the boys were being punished for sexually abusing kids.

“These were the victims of a brutal, heinous crime,” Lt. Timothy O’Neill told The Post about the tragic brothers, explaining that the sex-abuse allegations emerged because of what the parents told hospital officials. “There is absolutely no evidence that [Lucas and Christopher] molested children.”