I do have to wonder why we didn't get to see 17's family. My two guesses are that they just haven't made designs for them yet or maybe his wife will be an existing character and that will be a reveal later.
Gohan surpassed Goku's strength from the beginning of Z as a toddler, Goku got massively stronger training for 6 days on his way to Namek, Piccolo got stronger than second form Freeza by fusing with a Namekian that couldn't even touch first form Freeza, Vegeta became a Super Saiyan just by training by himself, Gero made 6 androids stronger than Freeza using data that ended after the Saiyan arc, Goten and Trunks became Super Saiyans as small children just cause.