Luke is Phil's youngest poo and only male child. He bases his relationship with his son on his own relationship with his father Frank - he saw his dad as a more of a buddy and close friend than a parent while growing up, and so wanted Luke to see him the same way. As they are the only two males in the family, they form a really close bond with each other and are often seen coming up with various schemes and ideas to try together. He loves a lot Luke and viceversa, as in many episodes it has been shown his family love towards him:
In the "Pilot", Phil has to shoot Luke with a BB gun because he shot his sister with, Alex, with that gun. But when he is just about to shoot Luke, Phil sees that he is scared, thinks that he has learned the lesson and he decides to not shoot him, although he accidentally ends up shooting him.
In "Fears", Phil tries to retrieve Luke's toy truck, even though he is scared of going there.
In "The Late Show", Phil reveals that of his 3 children, Luke is his favorite.
Despite having so much in common and relate very well, they don't have exactly the same likes and dislikes:
In "Fizbo", it is revealed that Phil is afraid of clowns, while Luke loves them. His fear is said to stem from finding a dead clown in the woods.
In "The Butler's Escape", Luke is not interested of being a magician, which disappoints Phil, because he loves magic, but he finally tells Luke that whatever he decide, he will always support him.
In "And One to Grow On", Phil wants to set Luke on a dance class, which he dislikes, because Phil says that he comes from a long line of dancing Dunphys.
Jay is Phil's father-in-law. He tries really, really hard to gain approval from Jay and Jay is very stubborn at not giving him any. It is almost as if Jay doesn't like Phil at all, but Jay tells Phil directly that he liked him. Once to Jay's dismay, he accidentally told Phil that he loved him, but Phil was too busy and didn't hear it. Jay introduces Phil as "Phil is my son-in-law," but Phil says it sounds like he is saying, "Phyllis, my son-in-law." Phil also complains that Jay says "Dumb-phy" instead of "Dunphy." Phil once fixed Jay's printer and since it is Phil's only accomplishment with Jay, he brings it up every chance he gets.
Gloria is Phil's step-mother-in-law. He has a crush on her, once staring at Gloria through Claire's sunglasses. Gloria is seemingly oblivious. Jay says nothing of it because Phil knows not to cross the line, saying he would never stray away from Claire. He takes any and all chances to hug or touch her, except once when he realizes that Claire is the most important thing that ever happened to him. But this quickly changes back.
They have not spent much time together, but when they have, Phil treats him almost like a son instead of a brother-in-law, which he is.
Mitchell is Phil's brother-in-law. They don't spend much time together, but they treat each other like brothers.
In "Strangers on a Treadmill", Mitch tries to tell Phil that his jokes for the the SCARB (Southern California Annual Realtors Banquet) are unfunny, but Mitch can't go through it after seeing Phil's sad face.
In "Tableau Vivant", Phil has to find a way to tell Mitch, that he is fired from his part-time job at the real estate agency. When Phil goes to Mitch's house to tell him about his dismissal while Mitch also tries to tell him that he does not want to continue working at the estate agency. Mitch bails out and he does not say anything and Phil believes that Mitch understood what he was trying to tell him. When Mitch appears at the agency later, Phil no having other choice, he finally tells him. Mitch is stuck in the elevator for two hours knowing he has been fired. The idea of losing his job does not seem to thrill him since he has never been fired before in his life.
In "Airport 2010", Phil drives Mitchell to retrieve his wallet, which he forgot at home in all the chaos.
Phil and Claire have been married for 20 years, as in "A Fair to Remember", they celebrated their 20th wedding anniversary. He acts as a foil to Claire's uptightedness and need to stick to rules. Although they are very different in personalities, it's clear that he really loves her and continuously makes an effort to let her know that, although sometimes that backfires as he has a tendency to mix things up, thus sending off the wrong meaning. Claire loves him too, but often refers to him as her fourth kid, as he has a tendency to act childish in a goofy and impulsive way. Although he loves Claire, he is seen to be easily mesmerized with beautiful women, especially Gloria; however he does state that he would never stray from Claire. They compliment each other's parenting style and are incredibly supportive of each other, whenever needed.