Be rather hard to prove. If the mainstream is right, Jesus didn't have children. No DNA. If they're wrong,it's been 2011 years or so since he was born and slightly less since he dies. I don't see useable DNA surviving that long. Of course allow me to qualify,I'm a first year college student and long time mechanic/laborer so I know jack-all about DNA.
The bottom line is, you're not going to convince them. If you could prove it scientifically, ther will always be someone who'll claim that it's a vast conspiracy to "Destroy Christianity." It makes no difference to the message that Christ taught us. Just my deux centimes worth, Neil