That's not exactly true. there was a super saiyan god before goku and vegeta. they r just currently the only saiyan gods, that we know of. and it's quite obvious that saiyan need a tail to go ape as that was stated several dozen times thre the dbz series @worldofelites19
@TristanBlackmon When I said that only Goku and Vegeta could go Super Saiyan God, I meant in canon, they were the only ones to ever reach it, not counting the.... less than 1%, I'm guessing of the entire Saiyan race through out history, that the legends are based off of.