Lynn Loud, Sr. (or Dad) is the father of Lincoln and his sisters. Lynn Sr. is a supporting character in the first season, and a major character from Season 2-present.
Lynn Sr. is stern, and often calls a halt to his kids' fights, but he loves and cares about them. He also loves his wife, and often acts playfully romantic towards her. He has been shown to have a childlike side at times, even sometimes taking part in his kids' antics, when it's all in good fun. He's also the more sensitive of the two parents, often necessitating his wife, and stepping in whenever he needs to pull himself together.
He's also shown to be quite a coward, as he screams and faints at the sight, sound, and idea of spiders, Lana's mud wrestling, horror movies, and Halloween.
Lynn Sr. wears a sea green sweater over a light-green checkered collar and cuffs, and brown slacks. He has a long pointy nose, brown eyebrows, and curly brown hair that is thinning on the top.
In "House Music", when he is playing the cowbell, he wears a yellow-striped shirt, and green pants which his underwear was seen. In his youth, he sported a mustache. His hair was also straighter and parted in the middle.
His personality is very similar to that of Tom Harper from Nicky, Ricky, Dicky & Dawn, as well as Harold Buttowski from Kick Buttowski: Suburban Daredevil, who are also father characters played by Brian Stepanek.
It is revealed in "House Music", that he used to be in a band, but got kicked out due to playing his cowbell too much, even when they were not practicing.