Note: because non-canon sources such as The Lives of Dax provide information that directly contradict show canon in many places, this will be derived mostly from information given in the show.
The Dax symbiont wss born in 2018.
Presumably, the symbiont then spent a long amount of time growing in the Breeding Pools.
Lela Dax, the first host, was joined in 2168 at the age of 56. The symbiont is now 150.
Lela was a legislator, and one of the first women ever appointed to the Triil Council. She had at lest one child, a son named Ahjess.
Lela died at the age of 114 in 2226 and Dax was joined to Tobin Dax. The symbiont is now 208.
Tobin was an engineer. He was also a vegetarian, never got drunk, bit his nails, and tried his hand at magic tricks and botany. At some point he met the exiled Cardassian poet Iloja. He had at least one child, named Raifi.
It is unknown when Tobin died and the symbiont was joined to Emony Dax. However, Emony met Leonard McCoy while he was in college, placing their interaction likely in the mid-2240’s (McCoy would have been 18 in 2245). Therefore it is probable that Emony was joined some time in the early 2240’s.
Emony was a gymnast and stood on her head to relax, but little is known about other aspects of her life. However, Jadzia’s statement that Dax had been a mother three times, combined with the fact that there were only 3 female hosts before her, implies that she had at least one child.
It is unknown when Emony died and the symbiont was joined to Audrid Dax. However, taking biological information of Audred into account, it is likely that this happened in the early 2260’s at the absolute latest.
Audrid became the head of the Trill Symbiosis Commission. She had at least two children, Neema and Gran.
Audrid died in 2284 and Dax was joined with Torias Dax. The symbiont is now 266.
Torias was a pilot. He had extensive combat experience. He was married to Nilani Kahn, but no children were ever mentioned.
Torias was killed in a shuttle crash in 2285 and the symbiont was passed to Joran Dax.
Joran was a musician. He became unstable following his joining killed at least 3 people. He had a brother named Yolad.
The Dax symbiont was removed from Joran, given a memory block, and joined to Curzon Dax later in 2285. The symbiont is now 267.
Cuzon was an acclaimed ambassador. He had a great understanding of and respect for Klingon culture, and therefore represented The Federation at the Khitomir Accords in 2293. He had a reputation as a womanizer. He served as a mentor to Benjamin Sisko starting in the early or mid-2350’s. As a field docent, he “broke” several Initiates.
It was never stated that Curzon Dax had any children. However, according to Jadzia, the Dax symbiont had been a father twice. Because it is established that Tobin Dax had children, either Curzon or Torias must have been the other father (at the time of Jadzia’s statement the memory block on Joran was still in effect). Given Torias’s short life and Curzon’s reputation, Curzon is the more likely candidate. He was most likely not married, however, since Jadzia later said that Dax had been a groom twice - Torias was known to be married, and it’s likely that Tobin was as well.
Curzon died in 2367 and Dax was joined with Jadzia Dax. The symbiont is now 349.
Jadzia served as the science officer aboard Deep Space Nine, where she was reunited with Sisko. She dated several individuals before beginning a relationship with Worf, who she would marry. She fought at the front lines of the Dominion War in the early 2370’s.
Jadzia was killed in 2374, and during transport Dax had to be suddenly joined with Ezri Dax. The symbiont is now 356.
Ezri had been serving as a counselor aboard the USS Destiny, but after once again meeting Benjamin Sisko she transferred to DS9. In 2375 she entered into a relationship with Julian Bashir.
The Dax symbiont was last seen in canon in 2375, at which time it was aged 357.