MADISON, WI -

The father and brother of a 5-year-old boy killed in a suspected child abuse case have been charged with sexual assault.

Anthony Turnbill, 35, of Madison, is charged with repeated sexual assault of a child. His son, Tyler Turnbill, 17, of Madison, is charged with two counts of repeated sexual assault of the same child and second-degree sexual assault of a child.

They appeared in Dane County Court for an initial appearance Monday morning and were released on a signature bond. Anthony Turnbill told news 8's sister station, WISC the allegations are untrue. He said his children are safe in his home, but are living in foster care now.

A criminal complaint states a girl told authorities about the alleged assaults on Oct. 7. She said the assaults occurred numerous times over several years.

In an unrelated case, the Dane County medical examiner ruled on Friday that 5-year-old Brayden Turnbill’s death was a homicide. Police have not said if there is a suspect in the case. Anthony Turnbill told WISC he knows who killed his son, but Sun Prairie police won’t confirm who might be held responsible.

Authorities were called to a home on Barrington Circle Tuesday afternoon and had opened a child abuse investigation.

Turnbill said he hadn’t seen Brayden in a couple of years. The boy’s mother had custody of him and Brayden had been living with her and her boyfriend.