A 27-year-old Brooklyn man was sentenced yesterday to 25 years in prison for teaming up with his girlfriend to beat her 4-year-old son to death.

Steven Dadaille and Myrna Chenphang, 26, pleaded guilty to first-degree manslaughter. They said they repeatedly hit little Jayden Lenescar with their hands and a belt buckle over two days in their Crown Heights home because he was touching his genitals and wouldn’t say who had taught him to do so.

Jayden was pronounced dead at Kings County Hospital on Oct. 23, 2009.

Chenphang will be sentenced on Jan. 19.