STURTEVANT – Two brothers serving time in prison together were charged Thursday with incest. A prison guard found Brian and Jeremy Threlkeld, both of Kenosha, engaged in sexual activity in their prison cell at the Racine Correctional Institution on March 31, according to a criminal complaint. The brothers had shared a cell for about two months. In an interview with police, both Threlkelds said they had sex three to four times per week while sharing a cell. Both said the sex was consensual. Both brothers are serving time in prison for the sexual assault of a child. Brian, 25, was sentenced to 10 years in prison in 2000. Jeremy, 21, was sentenced to 6 years in prison in 2004. If convicted of incest, each brother could be sentenced to an additional 18 1/2 years in prison.