The Sindacco family is another Italian-American Mafia family which is based in Las Venturas, and, formerly, Liberty City, where they originated. The Sindacco family also had a stake in Caligula's Casino, alongside the Forelli and Leone families. The Sindacco family wanted to do business with the Leone family and unite the two organizations, and this involved Don Salvatore Leone pledging 5 million dollars to the Sindacco family, which Salvatore reluctantly agreed to. Both outfits argued over who should run the casino, and so Ken Rosenberg (once working with the Forelli family, but then abandoned by the very powerful Vercetti Gang) was put forward as a neutral party. Ken was in the middle of the Three Families, so if one attacked the other, Ken would most likely be the target of revenge.
The Sindacco family was formerly represented by Johnny Sindacco, the Underboss of the Sindacco family, who would die from shock-induced heart failure in GTA:SA after meeting Carl Johnson for a second time. It was revealed that Johnny had previously been captured by the San Fierro Triads, tied onto a car driven by Carl and scared into revealing information. He then went into a coma, suffering a period of psychological and physical trauma. The Introduction prequel also indicates Johnny is in fact the son of the Sindacco's Don, most likely Paulie Sindacco, as he mentioned that his father wanted to unite their organization with the Leone family. It is suspected that after the Leone family abandon Caligula's Casino and return to Liberty City that the Sindaccos move in and re-take the casino, however there is no proof of this.
By the end of 1998, Don Paulie Sindacco decided to expand further throughout Liberty City, moving into Leone family territory in Chinatown, dealing drugs. In Liberty City Stories, on orders from Salvatore Leone, Toni Cipriani used J.D. O'Toole, who was running Paulie's Revue Bar in Liberty City's Red Light District for the Sindacco family, as an inside-man to help weaken the Sindacco family and claim the Red Light District and Paulie's Revue Bar (renamed Sex Club 7) as Leone territory. Later on, Toni Cipriani would kill Paulie Sindacco, the Don of the Sindacco family, in 1998.
After their defeat by the Leone family in the First Gang War of 1998, the Sindacco family left Portland for Staunton Island, moving into Forelli family territory. This resulted in the Second Gang War of 1998, this time between the Sindacco and the Forelli families. Don Franco Forelli and Don Paulie Sindacco attempted to establish a truce between the Forelli and Sindacco families, possibly to defeat the Leone family together. Before a truce could be created, however, Toni Cipriani uses a remote control device to assume control of Paulie Sindacco's car and run over dozens of Forelli family members with it. This fueled the Sindacco family war with the Forelli family, which doesn't end until the assassination of Paulie Sindacco in Shoreside Vale later that same year and the (possible) death of Franco Forelli in the Little Italy explosion, all caused by Leone family Caporegime Toni Cipriani. The Sindacco family also owned territory in Torrington, including The Big Shot Casino, until the Yakuza decided to expand their influence in Liberty City by taking over Torrington, and in the process The Big Shot Casino as well, and subsequently they changed its name to Kenji's Casino after his older brother's (Kazuki Kasen) death.
With no turf or front companies whatosever remaining in Liberty City, the Sindacco family have very little influence (if any at all) remaining in Liberty City by GTA III. The family's fate remains unknown, as their activity outside Liberty City after Paulie's death is never disclosed.
In GTA:LCS, Sindacco members wear black shirts, black pants and brown jackets (leather or not) with/without sunglasses and carry pistols. In GTA:SA the mobsters (presumed to be the Sindacco family) dress in either brown leather jackets with gray pants, light blue shirts with chains or in black jogging suits.