First of all, I'm pretty new to Genealogy/Ancestry.com

My paternal grandfather was named Albert Hobgood when he married my paternal grandmother (Ethel elia Beasley) in 1921 in Texas. However, according to family lore, he was born David Claude Pemberton in 1891 in North Carolina. I'd love to find out when and why this happened but I'm coming up short. Can anyone give a newbie some pointers?