Question: what is broly to goku?
Answer: The original version of Broly was born on the same day as Goku (kakarot), and had a power level of 10,000 (greater than most elite Saiyans). ... Broly eventually rages out and this leads to a small battle, to which Broly is able to overcome the mind control device and explode into his true form, the Legendary Super Saiyan.