Two teens who had attended Abraham Lincoln High School pleaded guilty Thursday to fatally beating a 57-year-old homeless man last year in Holmesburg, a spontaneous attack against a transient neighborhood native described by his brother as "a gentle and harmless soul."

Brandon Conrad, 15, and Malik Page, 17, admitted in consecutive hearings to participating in the deadly assault on Kevin Cullen, who grew up blocks away from where he was killed.

Conrad pleaded guilty to third-degree murder, robbery, and conspiracy, and was sentenced to four years at a juvenile placement facility and 15 years on probation — below the sentencing guidelines for adults charged with those counts. Assistant District Attorney Chesley Lightsey said Conrad's age influenced the recommendation, as did the fact that he threw an opening sucker punch but did not continue assaulting Cullen.

Page, meanwhile, pleaded guilty to the same charges and received a prison sentence of 12½ to 25 years for stomping and kicking Cullen in the head and face after Conrad's opening blow.

A third codefendant, Emmanuel Harris, 18, awaits trial.

Cullen's relatives said at Thursday's hearings that they were devastated by the crime. They said Cullen was an intelligent and well-liked son of Mayfair, one of six children, a graduate of Father Judge High School, and a valued neighborhood resident even as he struggled with mental health issues.

"He was a gentle and harmless soul," said Cullen's brother, Thomas. "Kevin was not anonymous."

Conrad, Page, Harris, and a teenage girl who later served as a witness and was never charged were wandering the neighborhood on the evening of Nov. 26, 2017, when they spotted Cullen on the 4200 block of Loring Street, according to Lightsey. The teens surrounded Cullen, Lightsey said, at which point Conrad threw a sucker punch, akin to a blow from the infamous "knockout game," knocking him to the ground, and Page stomped and kicked Cullen's body and head. Afterward, Lightsey said, the teens went through Cullen's pockets but found nothing to steal.

Cullen was taken to Aria Torresdale Hospital, where he was declared dead the next day.

The three teens were arrested in December. Police said afterward that a witness reported hearing Cullen's head hitting a brick wall during the attack, while others said the boys laughed after leaving Cullen behind.

Both teens apologized to Cullen's relatives during their court hearings Thursday. Page, gripping his head in his hands, broke down after expressing his regrets.

"I was just being stupid," he said. "I didn't mean to do it."