Josh Powell was the prime suspect in the 2009 disappearance of his wife Susan, but even after a tragic murder-suicide that killed both him and their two young sons, the case is far from closed, and RadarOnline.com has exclusively learned that some family members believe Josh's father, Steven Powell, was actively involved.

“I believe that at a minimum Steven knew something about what happened to Susan,” Kirk Graves, who is married to Josh’s sister Jennifer, told RadarOnline.com in an exclusive interview.

The families of Josh and Susan Powell are currently making the sad trip west to attend the funerals of Charles, 7, and 5-year-old Braden -- the two boys whose lives were tragically cut short by their dad on Sunday, and RadarOnline.com talked to one relative about his fondest memories of the children.

“Charlie was the smart one, the one that loved to science and art,” revealed Powell’s brother-in-law Kirk Graves in an exclusive interview with RadarOnline.com as he was driving from Utah to Puyallup, Washington for the funeral.