Regarding my heritage-how did i get to be a thornton?my name is terry robinson born in detroit mich.?

i was told my family was formerly from the benning-thornton family..if able please explain!! my family is from georgia and now resides in mich. i live in det. mich. am 63-have 4 sisters who were robinsons-1 child and are divorced! on my fathers side they were people named king