Thanks, I now have records of conviction in 1819 (David), although not the circumstances, and I have convictions (along with accomplice David Roberts), Justicia in Woolwich, Isabella to VDL Jul-Nov 1833, three convict musters, Tickets of Leave ('41 & '42) and pardons ('42 & '47). The Edward "Challnor" death in '61, Vic. is as close to finding anything that matches both Edward and the Police Gazette notice.
As far as the rest of their families - I have substantial info on their sister Christina Challenor Richardson's descendants, and both David's wife Jane Tiltson's ancestors, and their [only child] son James' descendants - which include me.
Missing info on Edward's wife and daughters [ignoring infant death of son] - all I have is unsourced names and dates ... ditto for Edward and David's parents.
My main interest in David is his history pre 1819 and post 1842 - the circumstances of his trial for Murder/manslaughter and if there was any sign of him in the Aust. colonies after his pardon.