A former volunteer at a northwest suburban church has pleaded guilty to sexually abusing two more developmentally disabled boys, prosecutors said.

Robert Sobczak, 20, of Hoffman Estates, was sentenced in Cook County court Tuesday to seven years in prison after pleading guilty to molesting a 15-year-old at a birthday party and an 8-year-old at Willow Creek Community Church in separate incidents.

The admission followed an earlier guilty plea by Sobczak in a case involving another boy at Willow Creek.

The victims in all three cases were special needs children, prosecutors said.

Other charges, including kidnapping, were dropped in exchange for his new guilty plea to a charge of aggravated criminal sexual abuse. He received the maximum sentence for the Class 2 felony.

In December, Sobczak had pleaded guilty to molesting another 8-year-old child with special needs while the child was in Sobczak’s care at the South Barrington church in early 2013. Sobczak received probation in that case.

Sobczak was a volunteer in Willow Creek's Special Friends program for children with disabilities when he took the boy to an isolated area at the church and fondled him, prosecutors said. Church officials said they notified authorities that day, leading to an investigation and Sobczak’s arrest.

Earlier this year, Sobczak was charged with molesting a teenage boy with a developmental disability during a birthday party in Schaumburg in March 2013.

Then on May 5, Sobczak was indicted on charges of aggravated criminal sexual abuse, kidnapping and unlawful restraint stemming from allegations that he abused a second boy at Willow Creek church. That incident came to light after civil lawsuits were filed against Sobczak and the church by the parents of the victims, officials said.

Sobczak has been in custody since March when he was arrested for molesting the teenager.

Officials at the so-called megachurch have said that they made changes in how they train and monitor volunteers in response to the two cases involving Willow Creek children.