Amazon’s CEO Jeff Bezos and Facebook founder Mark Zuckerberg are closing in on frontrunner Bill Gates to be the world’s richest tech billionaire, as their fortunes increase by $15billion each.Bill Gates, co-founder of Microsoft, who still holds the top spot with a fortune of $84.5billion, is been given a good run for his money by the younger men Bezos, 53, who has a fortune of $81.7billion and Zuckerberg, 33, valued at $69.6billion, according to Forbes list revealed on Wednesday.Both Zuckerberg and Bezos are the first and second biggest gainers this year, respectively, each increasing their extraordinary wealth by $15.5billion.Photo Credit: Getty