Lynn is the fifth oldest child of Loud Industries Senior Executive Vice President Lynn L. Loud Sr., and the youngest of Lincoln's five older sisters. Like both Richard and Lynn II, she has an annoying habit of turning everything into a sport. She is the third youngest shareholder of Loud Industries after Lisa M. Loud and Lincoln Loud.
Like Richard and Lynn Loud II, Lynn Jr. is athletic and competitive and enjoys roughhousing with her siblings. She practices every existing sport: football, soccer, basketball, baseball, etc. Also like Richard and Lynn II, Lynn Jr. tends to turn everything into a sport, which both their siblings consider to be their most annoying habits. Unlike both Richard and Lynn II however, she acts immature sometimes, much to their dislike.
Lynn has thick brown hair pulled back into a short ponytail. She wears a red and white jersey with a red "1" on it, red-and-white shorts, and cleats with striped knee-high socks. She is slightly taller than Lincoln, and has freckles on her cheeks.