Son Goku

Age at the begining of Dragon Ball: 12
Age when Gohan was born: 18
Age at the begining of Dragon Ball Z: 23
Age when he met Vegiita on earth: 24
Age when he turned super Saiya-jin for the first time: 25
Age when he met Mirai Trunks: 26 1/2

Adopted grandfrather: Son Gohan
Wife: ChiChi
First son: Gohan
Second son: Goten
Fater in law: Ox King
Best friend: Krillin
Brother: Radditz
Dauter in law: Videl
Granduater: Pan

Special note:  Goku is the first to go super Saiya-jin
and is also the first to go super Saiya-jin 3
He is always said to be the strongest but I disagree in some cases.  Like when Gohan's power level goes above his on the movie dead zone and while fighting Raddiz, Piccolo's power level also surpasses his during the fight with Radditz

Power Level (by age)
12..........I guess about 125-265
23..........320 - 980
24..........8,000 - 32,000
24 1/2....180,000
25..........1,500,000
28..........4,500,000
28 1/2....28,000,000
35..........34,500,000