Trunks is the son of Bulma and Vegeta. Half Saiyan and half human, just like Gohan and Goten. Trunks was surrounded by a scientific enviroment. Having his mother and grandfather as scientists, Trunks became very intelligent at science.In the future, Trunks and Goten were battling the androids, but they were too strong, Bulma had completed a time machine and sent Trunks back to help Gokou and Gohan fight. This is the story of Mirai (Future) Trunks, who is pictured right.
Another version of Trunks is the small child version, Chibi Trunks. In most of the Dragonball Z series, Trunks and Goten fight side by side and they are in the Broly story and the "Fusion Form:Gokou and Vegeta" movie as well. They are in others too.
Trunks is famous for killing Freiza by slicing him in half. This was Trunks' first appearance on the show. Of course, he is one of my favorite characters on the show.
He was also one of the stars in the third and final dragonball series, Dragonball GT. Dragonball GT was about the journey around space that Trunks, Gokou, and Pan had traveled in search of the Dark Star
dragonballs. Which is why GT stands for Grand Tour. In one hilarious episode, Trunks is forced to dress as a princess to marry some beast.
More information still to come on the biography page about Trunks.
Gohan
More information still to come on the biography page about Gokou.
More information still to come on the biography page about Piccolo.
More information still to come on the biography page about Vegita. 
Gohan is the second most important character in dragonball. His father, Gokou is the most important. Gohan grows from a little child of 5 to a grown up of 25 in the series. A picture of him when he was 9 and in super saiyan stage is pictured right. Gohan's 15 minutes of fame was when he destroyed the great villain, Cell with one single punch.
Another identity of Gohan was as the great Saiyaman. He defeated everyone in a tournament and then unmasked himself as Son Gohan. Gohan was trained by the nameccian Piccolo. Piccolo was first in the Dragonball series as a villian but then switched to the side of good. He never really liked Gokou, but he did take a liking towards Gokou's son, Gohan. He trained him and in the Vegeta saga, took a big punch intended for Gohan by Vegeta's right hand man, Napa. The two got closer together as the series went on, and in one part, Gohan sings a song to Piccolo about how much he admires him, while Piccolo looked on, insulted by this saiyan warrior singing a song.
Later in the series, Gohan began going out with the daughter of Mr. Satan, Videl. Later on the two got married and had a daughter named Pan.
Son Gohan also made an appearance in Dragonball GT. In the Baby saga, Baby takes over the body of Gohan, and Gohan hits Piccolo with a kamehameha while Piccolo retreats and carries Goten to safety.
More information still to come on the biography page about Gohan.
Goku
His real name is Kakaroto. He discovered that from his brother Raditz which is also the first time he learned that he is a Saiyajin. Not only is he a great warrior, but also a spectacular leader. Throughout the entire series, he had inspired many, including both of his sons, Gohan and Goten and especially Vegeta. He is a diligent and hardworking person who would never fail to take on new challenges. Even though he had became the most powerful warrior in the universe by defeating Freeza, he still strive to become better. After Future Trunks had foretold the arrival of the cyborgs and Dr. Gero. He could have opted for the easy path by getting to Dr. Gero before the cyborgs were created, but he chose to challenge himself instead by preparing for their arrival. Goku’s unfaltering spirit and confidence is remarkable. After he forfeited the battle against Cell, no one, not even Gohan himself had the confidence to defeat Cell. Goku was the only one who had confidence in Gohan and followed through all the way to the end, even after Gohan was seriously injured and lost the will to fight. He never quits under any circumstance. Even after everyone gave up, his mind never stopped looking for solutions. Seconds before Cell was about to explode and destroy Earth, Goku realized he could teleport Cell to another location. His leadership and inspiration was proved pivotal as Future Trunks unveiled the grim story of his time where Goku died of a rare heart disease and everyone except for Trunks were killed. The most tragic of all was that Gohan’s tremendous talent was never realized as he died under the hands of #17. After the Dragon Ball Warriors initial encounter with #17 and #18 and subsequently Cell, Goku realized that he must transcend the Super Saiyajin to stand a chance against the cyborgs. Under his guidance, an intensive training program in the "Time Room" was launched. During that time, he trained Gohan for the first time and fully unleashed Gohan's potential. The one person he had inspired most throughout the series was Vegeta. Vegeta entered the story as as an evil individual who would find any means necessary to satisfy his hunger for power who was also too proud to accept defeat. Through Goku’s inspiration, Vegeta slowly transformed into a good hearted person who accepted himself. During Goku’s final battle with Majin Buu, he openly accepted that he was no match for neither Buu nor Goku and willing to participate in the sidelines (by gathering energy for Goku’s final strike) rather than the actual fight.
Piccolo
He is one of the characters who was originally evil, but through a series of unexpected events, the evil in him was slowly washed away as Piccolo took different forms. Piccolo is the offspring of Daimon, who was the pure evil which separated from Kami-sama as another body. Piccolo and Kami-sama is one person in two bodies. If one of them die, both will die. When Daimon was killed by Son Gokou, he vowed that his offspring Piccolo will avenge him. Thus, Piccolo's character is not just pure evil the way Daimon is. He is simply focused on destroying Son Gokou. The two of them first met in the Budokai. Because of the arrival of Raditz, Piccolo found himself an unwilling partner of Son Goku and together defeated Raditz. When he learned that two more poweful Saiyajin will avenge Raditz, Piccolo only found himself even more unwillingly on Goku's side by volunteering to train his Son, Gohan to become a warrior to fight against the Saiyajin. Piccolo's militant training style made Gohan a stronger person, gradually unleashing Gohan's tremendous talent. During the time he spent with Gohan, Piccolo began to develop love and care for Gohan, which was fully realized when he sacrificed his life for Gohan in the battle against Nappa. His love and care for Gohan is readily apparent throughout the Freeza and Cell series.
Vegeta
Even though he is evil at heart, Vegita is perhaps one of the most strong-willed characters in the series. Like Son Gokou, he is extremely industrious, constantly striving to be better, but different purposes drove Vegita's spirit. Gokou fought to defend the lives and others and to challenge his limitations while Vegita fought to satiate his bloodthirsty appetite and die hard pride, which is unwilling to accept defeat. This gradually changes throughout the series. The primary driver of his will is Son Gokou. Vegita's defeat in his first encounter with Gokou and his unwillingness to accept Gokou being more powerful had constantly fuelled his strong will to continue to train himself. After seeing Gokou turn into Super Saiyajin and defeating Freiza, he grew even more jealous of Goku’s achievements and immersed himself in intensive training. After much sweat and frustration, he finally became Super Saiyajin. He only enjoyed a fleeting moment of pride in destroying #20, before being defeated by #18. Vegita’s first catharsis occurred during Son Gohan’s battle with Cell. Because of his rash decision to attack Cell when he did not have the power to, had caused Gohan’s arm to be seriously injured when Gohan saved his life. Not only was he not even close to Cell’s ability, but also served as a hindrance to Gohan. That was the first time Vegita accepted his incapabilities by making an apology to Gohan. By the time Majin Buu appeared, what used to be a cold-hearted Vegita changed. Right before he proceeded to sacrifice his life in an attempt to destroy Buu, he told Trunks that he cared about him and how he felt bad about giving Trunks much less attention then Trunks deserved. During Son Goku's final battle with Majin Buu, Vegita goes through a complete catharsis. He realized that Goku's pure and kind heart gave Goku the power that Vegita never had. He finally realizes that the good ultimately prevails.
Goten
Goten is the second son of Gokou and the brother of Gohan. Goten and Trunks are best buddies. In a special movie, the two feel their fathers energy as they fuse into Gogeta, and they follow suit and fuse into Gotenks and perform a super ghost kamikaze attack. Like the rest of the Son family, Goten has a big appetite.
In the Broly story, Goten makes an appearance and helps out his dad, Trunks, and Piccolo get rid of Broly. In the final movie of the Broly story, it is up to No. 18, Trunks, and of course, Goten to finish the job as Jaguar genetically cloned Broly.
More information still to come on the biography page about Goten.