AP Photo/Jae C. Hong In this photo taken May 4, 2012, Republican presidential candidate, former Massachusetts Gov. Mitt Romney smiles at a campaign stop in Pittsburgh, Pa. Romney is a grandfather again, and he has a surrogate to thank. Tagg Romney, the presumptive Republican presidential nominee's oldest son, announced Friday that that he has newborn twin sons. Tagg Romney tweeted "big thanks" to the surrogate who gave birth to the twins, named David Mitt and William Ryder.