Paul Hennessy, is a former sports writer who worked from home as a Lifestyle columnist described as being "the master of the double standard" and a "Psycho-Dad", as well as a perceived hypocrite who often embarrasses his children, even if he wants what is best for them. Nonetheless, he loves his children, and wants them to have happy futures. Paul dies in the second season because of aortic dissection (the same ailment that claimed Ritter's life). He died in a store while buying milk.

Cate S. Hennessy is the wife, mother, nurse, and easily the most sane and composed person in the family. She takes a nursing job at the kids' school so she can work standard hours and spend more time with the kids. Cate starts dating her kids' high-school principal, towards the end of season three. During her teens, she was more or less just as popular, scheming, and rebellious as Bridget, thus she is usually the first to notice when Bridget is up to something. She received her middle name "Stinky" as a result of her father promising his best friend he would name one of his children after him after accidentally stabbing him with a bayonet while they were drunk in Korea; to hide this, she claims that the S stands for "Stacy."

Bridget Erin "Beach" Hennessy, is the beautiful, ditzy oldest child. She is depicted as a stereotypical blonde, a popular bombshell who is preoccupied with her looks, teenaged boys, and little else. She sometimes displays intelligence or profundity, but these are initially few and far between, yet often poignant. Her favorite book is J. D. Salinger's The Catcher in the Rye. After her father dies, she begins to steadily mature. Bridget initially felt guilty about Paul's death because the last words she ever spoke to him were "I hate you" after arguing with him earlier that morning, because he said no to her using the car. In season two, Bridget was revealed to have been conceived on a beach.

Jim Egan, is Cate's father. Jim served in the Korean War and is proud of his service (he angers whenever it is mentioned as a "police action"). He is very protective of the family. He often sneaks away to smoke tobacco. He is divorced, having formerly resided in Florida before moving into Cate's basement, and often used to try to beat C.J. with his cane. He takes pride in C.J.'s success as a teacher. When C.J.'s biological father comes to visit his son, Jim feels out of place and angry because he prepared a car for C.J. after he becomes a full-fledged teacher, but then Mr. Barnes gives C.J. a sports car.

Kerry "Care Bear" Hennessy, , is the middle child, but is not very happy about it. She is often seen as unattractive when compared to her beautiful older sister, Bridget. She was accused by Bridget of stealing her (ex-) boyfriend, Kyle, though clearly Bridget's actions drove Kyle away. Kerry is negative about most things and sarcastic, often making snide remarks about essentially everybody, though less to her mother. She is also a passionate activist who cares about animal rights. She lost her virginity to Bruno (her boyfriend in Europe) later in the third season. She is often annoyed at her sister and is easily upset, yet frequently the two girls team up against their parents' authority or at the expense of their younger rascal brother. Kerry is also very artistic and keeps a sketchbook. She is the smart child, but often shows naiveté. After she starts dating Bridget's popular ex-boyfriend Kyle, her own popularity increases, and she begins to act a little more like her older sister.

Rory Joseph Hennessy, is Cate and Paul's son and their youngest child. He constantly tattles on his sisters, getting twisted pleasure out of it, as per his remark when he had stirred the pot to his liking: "This is just like my birthday!" Usually he waits until his sisters already commit an infraction, then he tattles to see his father explode. Rory is his father's favorite, being the boy. He becomes involved in money-making schemes with C.J. He is commonly seen playing in the living room and mentions wanting a monkey, which he once had by trading some of his father's baseball cards; the monkey was later traded for a guitar, which was short-lived, as Rory annoyed the family with it. He also delights in showing his friends the private aspects of his sister Bridget's life, mentioning once that his friends looted Bridget's underwear drawer. Rory was hit hard by Paul's death and ended up punching a hole in his wall out of anger, cutting his hand. He covered for it saying he burnt it taking a casserole out of the oven. After he enters high school, Rory matures, leaving C.J. to be the wisecracker of the family. However, Rory still had his moments.

C.J. Barnes, , is Cate's nephew. He was once in the Army and claims to have studied aerial photography during the Gulf War, and to have received a Purple Heart in combat, which is in complete contrast with his generally childish attitude. He is a teacher at the school and often pursues women, albeit unsuccessfully. When C.J. first arrives, the family is initially surprised. He reveals to them that he was ashamed that he did not live up to be the person Paul had once said he would be and avoided them because of that. He lives along with his grandfather, Jim, in the basement (having previously lived in a van, which was burned by that same grandfather). He once dated Mrs. Krupp, his cousins' (Kerry and Bridget) math teacher, but he ended up cheating on her with his ex-girlfriend Cheryl. He once revealed that his first initial stands for Corey, but Rory said that was untrue. C.J. previously smoked marijuana heavily (and in fact used to smoke with Kyle's older brother), but at the start of his appearances, he claims not to have touched it in two years (he originally claimed it was five, though he relented after Jim expressed disbelief).

Kyle, is Bridget's – and later Kerry's – boyfriend. He is often seen spending time with Rory when not with either Kerry or Bridget. His father, Tommy, used to work with Paul.

Ed Gibb, is the principal of the local high school. He and Cate knew each other in high school, and even dated. When discussing it, their account of their first romantic encounter varied, with either believing they had more self-control and admitting to the other that they liked the other as just friends. Despite this, they have had some very intimate moments.

Coach Scott, , is a high-school coach on whom Bridget had a crush. He likes Cate, and Cate initially likes him, but then discovers Bridget's crush, which causes her to deny Scott's romantic advances towards her.

Jenna Sharpe, is Paul's boss Nick's daughter, and one of Bridget's rivals, who later becomes her friend. She has a younger sister, Rachael , who is a friend of Kerry.

Missy Kleinfeld, is Rory's love interest in season two. She has a sister, who likes C.J.

Jeremy, is Bridget's tutor and eventual boyfriend. He is considered a nerd at school, and because of this, Bridget at first denies her interest in him by saying it was only because he was her tutor.

Anthony W., is a student in Bridget's class. He was a white boy who spoke like a black rapper, often resulting in confusion. In "Cool Parent", he is shown to play lacrosse.

Maggie Barnes is Cate's sister and C.J.'s mother. Maggie shares the same sensitive, moody nature as Kerry. However, it appears (from a conversation between Ed Gibb and Cate) that Cate was the smarter one, as well as being more popular.

Fred Doyle, is a persistent and over-friendly neighbor of the Hennessys, and husband of Mary Ellen. He is the father of Donald "Donny" Doyle, who has dated Bridget for some time. Fred was the head of the neighborhood watch, and his family is revealed as religious when Bridget claims she is going over for Bible study in an episode in season two.

Mrs. Crupp, is a math teacher from school.

Damian, is Bridget's ex-boyfriend. He appeared in two episodes.

Lacey/Lacy, a sometimes friend of Bridget, appeared in three episodes.

Laura, is Cate's mother.

Cheryl is CJ ex girlfriend