Family:
The original Piccolo was spawned from Kattasu, so he could be considered his father.
Kattasu himself is a spawn of teh Great Elder, so he would be Daimao's grandfather.
Piccolo Daimao and Kami were created when the original Piccolo split in two, making Kami his twin brother.
Daimao spawns five sons: Piano, Tambourine, Cymbal, Drum, and Piccolo Jr.

Story:
Pre-Dragon Ball:
In 261 A.D., fierce storms were wiping out the Ajisa plants Planet Namek, and one member of the race decided to send his son off in a space ship so that he might escape death. That Namek was named Kattasu, and his son's name was Piccolo.

The stomrs eventually stopped, but no one pursuded Piccolo, and thus his ship eventually found it's way to earth due to problems that arose and a forced landing. What happened then is not clear, but 170 years after his departure, in the year 431, Piccolo began training under the current Kami.

In that same year, much happened to Piccolo. His master Kami had to pick a succesor, and was confronted by the demon known as Garlic. Garlic was angry for not having been picked to ascend to the throne, and was eventually defeated and trapped by Kami.

Kami then decided that Piccolo should become the next God of earth, but there was a small problem. Piccolo had evil in his heart, and had to rid himself of it before he could take Kami's place. To achieve this, he split into two seperate beings, purging the evil into a new self. The good half became Kami, while the evil half was named Piccolo Daimao.

Daimao showed off his bad-side often enough, creating a reign of terror across the earth. He was finally stopped by the martial arts master Mutaito, who used the "Mafuba" technique to seal Daimao within a denshi jar at the cost of his own life. Making sure his master's sacrifice would not be in vain, his best pupil, and now strongest man in the world, Roshi, tossed the jar into the deepest part of the ocean, where it would remain for almost 200 years.

Dragon Ball
Daimao was freed to wreck havoc once again, when he was freed by the villan known as Pilaf and his assitants for their oewn purposes. Striking a deal with the demon king, Pilaf wanted to collect the mystical dragonballs for his own desires.

On May 7th, 753 AD, the worst fear of Muten Roshi came into being when his pupil Kuririn was killed, and a piece of paper with the word "___" was found. The tenkaichi announcer reported that a m Gokou immediately took off, seeking vengence.

Although he was warned against doing it, Piccolo spawned another child, Cymbal, to aid in the search for the Dragonballs. He was quickly killed off(and eaten) by the swordsman Yajirobe. Sensing the death of one of his children, Piccolo quickly went to their location, where Son Gokou had just finished off another one of his children, Tamborine, who had previously killed Kuririn.

Yajirobe knew who Piccolo was, and wisely fled. Gokou, still seeking revenge, challanged the Demon King to a duel, where he got beaten quite badly, and was assumed dead by his family.

more to come!