I have an 8 month old son and he has 2 potential fathers one of which is on his birth certificate we are not married or engaged just living together and he and his parents ordered a DNA test online and done the test on my son without me knowing or giving consent for this he did ask for my consent a few weeks prior and I said no to this.The email of the results show he isn't the biological father and it says on the form it is non leagally binding. I thought the mothers consent always had to be given when a dna is done.

NO... if there is a question of Paternity.. the father has every legal right to have this run to conclusively determine is he is or isn't the natural father.

He could even get the cort to order it (however only after the child has been born).

This because of parental rights as well as custody and child support issues.

A name on a piece of paper really means little (the mans name on it is frequently NOT the actual natural father)... because DNA test will definatively prove actual paternity.

Not sure where you got the idea that mother's consent was needed. Since he is on the birth certificate he has equal rights to the child. Therefore, he was within his legal rights to take a cheek swab and do the test. However, as noted this test is not legally binding. If he wants off the birth certificate and wants out of being the father he now has to go to court to challenge paternity.