That's correct, sam is Jimmy's other son.
Getting back to Johnnynono's question if Lombardo and Marcello recieved seperate trials would they have gotten off. I highly doubt it with the both of them. They had more evidence to convict Marcello with. Lombardo on the other hand they didn't have a lot to go on for a conviction. I think the only chance Lombardo would have had to get a trial with a partial jury would have been if they held it in another state where potential jurors don't know the history of Lombardo. Even the average citizen in Chicago knows the name Joey the Clown. Even if Lombardo was found not guilty the government would have kept coming after him until they would get a conviction on other charges or crimes he commited.
The reason the government went after these guys even in there old age is to send a message to the younger generation of mobsters that if you commit a crime at the age of 22 they will still go after you even if you are in your 70's. I bet Lombardo never thought in a million years that in the year 2005 he would be indicted for the Seifert murder.