What is the relationship between the original NIKO of GTA4 and the two DLC protagonists, and what is the relationship between the other two DLC protagonists?

The following is my summary of the complex relationship between the three protagonists in GTA4 series: the protagonist of GTA4 is Nick, an immigrant from Eastern Europe, the protagonist of Lost and Curse is Johnny, the second leader of new york Wild No.1, and the protagonist of Song of Nightlife is Louis, a nightclub shareholder and spectator. The relationship between them is very complicated. First of all, Nick once killed a speeding gangster, who seduced the daughter of Fangstin, the Russian gangster, and that guy was Johnny's brother. Nick's cousin Roman was kidnapped, and Johnny kidnapped him; Nick and Johnny cooperated in drug trafficking for the first time, but unfortunately they fell into the police circle and parted ways with deuex. Nick arrived in new york on a cargo ship, and the chef of the cargo ship smuggled diamonds. The earliest diamond seller was Louis' partner. Johnny (instructed by Mafia Ray) was the first to rob Louis diamonds in the diamond trade. Nick and Johnny once again joined hands to trade diamonds with Jews. Louis took the diamond halfway. After taking the diamond, Louis exchanged it for Grace kidnapped by Nick. Louis was one of the hostages when Nick and Peggy robbed the bank. The Russian enemy who has been chasing Nick was finally killed by Louis ... If my answer can help you solve the problem, please choose "solvable" and "original" to adopt. If not, please keep asking, and I will help you until the problem is solved.

I'm not talking on paper. This is a screenshot of my game. I refuse to quote it. -People announce that this is the same task GTA4 and different screenshots of loss and curse.