Prosecutors charged Patricia Butler and Billy Wilson with tampering with evidence.
Authorities say Butler and Wilson helped remove Jason Davies' body after he was killed at a St. Joseph apartment last week.
Prosecutors say Butler witnessed the murder then called her brother to help get rid of the body.
Davies' body washed up in the Missouri River near Leavenworth.
Prosecutors say Robert Jarrell and Martin Rilinger beat Davies with a baseball bat and frying pan before dumping his body in the river.
A third person, Dollie Williams, is also charged with tampering with evidence.