Garwood Simpson was the son of Rupert Simpson and Winifred Running Goat. He married Clowta Stillman and they had five children: Howland, Zeke, Pippa, Floyd, and Hiram. His siblings were Ivy, Galston, Prudence and Trixie. He is the great-great-great grandfather of Homer Simpson.
Behind the Laughter
Although Garwood is, according to The Simpsons Uncensored Family Album, Abraham Simpson's great great grandfather, Abraham has himself stated this role is filled by Virgil Simpson, thus creating a discrepancy in the family tree. It is likely that he, along with all the other generations prior to Virgil, are biologically related to Hiram and Eliza Simpson.