The Son'a are descendants of the Ba'ku, who left the Ba'ku colony world in the 2270s when their rebellion against Ba'ku philosophies failed. These renegade Ba'ku soon took on an air of narcissism and materialistic behaviour.
Following their departure from the Briar Patch the Son'a became a group of nomads, and soon earned a reputation for extreme aggression. During their travels they visited many planets and took what materials they needed to improve their existence. They were also known to subjugate weaker species and make them their slaves, as in the case of the Tarlac and the Ellora in 2325. Due to several sanctions imposed against them by the Federation Council, the slave races had allegedly been freed.
Despite following the wishes of several other spacefaring civilizations, the Son'a have also been known to act in defiance of treaties and agreements. The most essential treaty they have acted in defiance of is the Second Khitomer Accords which deal with the use of subspace weapons, and all Son'a battle ships are equipped with such weaponry.
Following the start of the Dominion War in 2373, the Son'a sided with the Dominion and started producing ketracel-white for the Jem'Hadar at several facilities, including Devos II. (DS9 episode: "Penumbra")
In 2375, the Son'a made an agreement with the Federation Council to set-up a duckblind mission to observe the Ba'ku. Ahdar Ru'afo and Admiral Matthew Dougherty made an agreement to remove the 600 Ba'ku to another planet so that they could access the life-prolonging power of the metaphasic rings. However, the plan was soon exposed by Lieutenant Commander Data who discover a cloaked holoship on the surface. When the USS Enterprise arrived to investigate, Captain Jean-Luc Picard also learned of the plan and successfully prevented it from being successful. (TNG movie: Star Trek: Insurrection)
Following the defeat of this plan, a number of Son'a were allowed to settle on the Ba'ku planet in a separate colony. Some of these Son'a, under the leadership of Urano, rebelled once again with Romulan assistance in a bid to seize control of the entire planet. The plan was put to a halt by Picard, Data and Ensign Sovok. (TNG video game: Hidden Evil)
Rogue members of the Son'a would continue to attempt to forcibly take over the homeworld of the Ba'ku but these would be repelled by Starfleet, who made sure to keep the world under their protection. On one occasion, the defense of the planet was commanded by Commander Worf. (TNG video game: Armada)