Welcome back - it's a familiar story!
As for Rico, the original Rico was Dredd's clone brother, who went bad and was sent to Titan by Dredd 20 years before the prog stories started - prog 8 (I think) saw him return to get revenge and get gunned down by Dredd. Apparently he fathered a child (Vienna) with a reporter who was allowed to interview him on Titan during his sentence.
The current Rico is another clone of Dredd, but one who is still one of the good guys - he chose to reclaim the name "Rico" and he's basically a younger model of Dredd.
For a collection of stories centred about Dredd's extended clone-family, try the TPB Judge Dredd: Brothers of the Blood.
Other essential Dredd catch up GNs - Origins (bad Bob
Trump Booth, the Atomic War and the the birth of Justice Dept) and Day of Chaos (payback for the Apocalypse War - MC1 devastated); but I'd also recommend The Pit (sector house procedural with large supporting cast) and Total War (Justice Dept vs terrorists demanding democracy)