Yes, Thomas Edison had six siblings, both brothers and sisters. Thomas himself was the youngest of all the seven Edison children.
Born in 1847, Thomas Alva Edison was the youngest son of Samuel Ogden Edison, Jr., and Nancy Matthews Elliott Edison. Edison's parents had six other children: Marion Wallace Edison (born 1829), William Pitt Edison (born 1831), Harriet Ann "Tannie" Edison (born 1833), Carlile Snow Edison (born 1836), Samuel Ogden Edison III (born 1840) and Eliza Smith Edison (born 1844). Thomas Edison never knew his brothers Carlile and Samuel, as they died before he was born. Carlile died in 1842, and Samuel died the following year. Eliza died in December 1847, when Thomas was just a few months old.