These are bios of most of the main characters in dbz. There might be more to come soon!
Gohan
Gohan Is Goku and Chi-chi's first son who is named after Goku's adoptive grandfather Gohan. He first appears in the series at 4 years old.Gohan is only half saiyan.In one day Gohan is kidnapped by Radditz, beaten up, his father gets killed, then Piccolo drops him in the middle of nowhere and is left to survive for six months. He goes super saiyan while training in the spirit and time training. During the cell saga/cell game goku reveals that gohan is stronger than himself and so makes him fight. Gohan evntually goes ssj2 when cells pushes it and hurts his friends. When Gohans dad or friends are being hurt gohan is enraged and beats up the person he is fighting for a while most of the time, so don't mess wit his friends! At the end of dbz Gohan is still a good fighter but he should be better. As he grows older he has less of an urge to train on his own. He kinda becomes a "nerd" but you still wouldn't wanna mess with him. Gohan finally gets married to a girl called Videl. They have a house next to Goku's and have a daughter named Pan.
Goku
Alright this guy is pretty much a nobody. He doesn't do much. He's only the main chracter through DragonBall/Z/GT. Nah, just kidding. Goku was born on the Planet Vegeta and sent to Earth to destroy the earthlings living on it, and prepare it for sale for Frieza. Luckily he fell off a cliff while he was wondering through the forest with his adoptive grandfather Gohan. He bumped his head on a rock and forgot his mission. Goku is a full blooded saiyan so he loves to have a good fight. When he gets older he marries Chi-chi and she later gives birth to their first baby which they name Gohan. After Gohan she later has another baby named Goten. Goku dies twice throught DragonBall. The first time is when Piccolo fires his Special Beam Cannon to kill Radditz while Goku holds him and Goku won't let go and so there for dies. The second time he teleports cell to King Ki's planet and cell detinates their so no one dies on earth. Goku gets wished back by the dragon balls the first time he dies then he is given back his life by Kaioshin. Later in GT Goku leaves with Shenron and it is not revealed if goku is alive or not. He is also the only character to reach every super saiyan level.(1, 2, 3 and 4)
Goten
Goten is Goku and Chi-chi's second son. Goten turns super saiyan at a much earlier age then Gohan or Goku because he was born when Goku was alot stronger. Goten is practically identical to Goku. Hair, face and all. When i first saw him i mistook him for chibi Goku! During most of his time in dbz he is only 7 years old but looks for strong guys to fight, and always looks for an adventure. Beleive it or not he goes balistic when he hears about this "Majin Buu" guy and can't wait to fight him. He doesn't really get much stronger after the Buu saga though. He doesn't bother to train any more like gohan.
Krillin
This would have to be the strongest monk i have ever seen! yes people krillin use to be a monk. He is a member of the Orinji Temple.You might be wondering why does he have those six little dots on his head? They are scars which are burned into the forehead of each member. Krillin is bold and ya wanna know why? Well he actually shaves his hair so that an opponent can't grab his hair in battle. During the seven years after the cell game he grows his hair back(his hair is freaky!)His wife is android 18 and they have a daughter named Marron(named after his old girl friend)
Future Trunks
Trunks seems to be the gals fave dbz character. I'd say they think he's cute. Trunks is introduced when Frieza-bot comes to earth to get revenge. He is killed by trunks. The main reason he comes to the past is to give Goku a heart disease medicine only in his time. With this Goku gets better when the disease kicks in. In Trunks' timeline Goku dies of it but Goku survives in normal time. Trunks stays around to help fight the Androids and Cell. He's a nice guy and everyone likes him.