Daniel Gatrell, 16, is being charged as an adult with two counts capital murder and one count arson in the deaths of Michael Palmer and his 2-year-old daughter Hannah Dowdie.
His cousin, Robert Gatrell was arrested last week.
Robert Gatrell's grandfather Charles Gatrell is also facing charges. Police say they served a search warrant at his property and he got combative and threatened them.
Police say they did find some evidence there, but did not release any details.
However, police are saying now that Palmer was friends with Robert and Daniel Gatrell, but still no word why he and his daughter were killed, or how.
Their bodies were found in a burned truck in Sweet Home in December.