Broly is a special case, its not even agreed as to wether or not hes even canon. As for Goten and Trunks thats explained by being sons of Super Saiyans. Gohan for example had to have his own 'breakthrough' because he was born before Goku went SSJ.

Nothings decided but i think its a little dissapointing to make SSJ so easy and meaningless just so you can play a certain charachter that couldnt fight his way out of a wet paper bag without it.