Ah, yes, the Dom Com. A celebration of the place we live, and the people with whom we share it. And, like anything else, can be written well...or poorly. Hopefully, this helps you write it well.
Step One: Meet The Family
First of all, what kind of family do you want? The standard Dom Com family is, of course, the Nuclear Family with 2.4 children (usually a a boy, a girl, and a baby of either sex) a stay-at-home mom, a Bumbling Dad, and a dog.
But, of course, families aren't always like that. Especially in this day and age of marriage, divorce, and remarriage, women working outside of the home, children born to parents in relationships but not legally married, etc. being commonplace. So, for example, you might have stepparents. Or a gay or lesbian couple with two point five kids and a dog. Or the Bumbling Dad may stay home with the kids while Mom goes out to earn the paycheck. You might have a newly-married couple that has no children yet, or a middle-aged couple whose kids have long since grown up and left the house. You might have a Mother of a Thousand Young. You might have a Missing Mom or a Disappeared Dad. You might not have a family at all, but rather True Companions living in the same house or apartment. The children could be toddlers, or adolescents. Be creative!
Most families in these types of shows are white, middle-class Americans from Flyover Country. There is nothing inherently wrong with this, but why not branch out a little? Your family could be rich. Or it could be working-class. They could be black, Hispanic, or Asian...or even space aliens. They don't have to live in a Big Fancy House in Suburbia. (More on Setting later.)
Step Two: What Kind of Family Is This?
Now that you've created your characters, how do they relate to one another?
In recent years, it's become commonplace to have the Dysfunctional Family featured in a Dom Com. This works because, well, let's face it. Nobody's family is 100% perfect all the time. If your family is too perfect, you run out of interesting plot lines, and the show gets vapid.
That said, however, don't rush out and turn your Dysfunctional Family Up to Eleven by making them into a Big, Screwed-Up Family. The Big, Screwed-Up Family is not the same as the Dysfunctional Family, at least not in TV-Trope-Land. The Big, Screwed-Up Family tends to lose sympathy with the audience, because most people can't relate to it. Such families are common enough that they're not unheard of (unfortunately), but not as common as you might think. Further, if Played for Laughs, a lot of times you'll be delving into Black Comedy, which does tend to put people off, even in this Darker and Edgier age. This too makes the show vapid and eventually unenjoyable. The Big, Screwed-Up Family should be reserved for when it's Played for Drama.
Therefore, for purposes of the Dom Com, the best type of family, regardless of who or what composes it, is generally a Quirky Household or a slightly Dysfunctional Family. What's the difference? Well, the Quirky Household is just that: quirky. (For example, a Nuclear Family of Otaku that's always in cosplay, but otherwise, a relatively normal, loving family. They have their day-to-day foibles, but nothing too "out there.") The Dysfunctional Family, on the other hand, consists of characters that frequently come into conflict with one another (though not necessarily violently), offset with the occasional Aww, Look! They Really Do Love Each Other moment. It could be argued that (at least in TV-Trope-Land), all dysfunctional families are quirky households when Played for Laughs, but not all quirky households are dysfunctional families. It works because you can write plotlines easily; just think of the day-to-day foibles, conflicts, and bloopers that happen in your own life, or the lives of your own family members. Because of that relatability, the humor is easier to find.
So, how dysfunctional is too dysfunctional?
The basic distinction between the aforementioned Big, Screwed-Up Family and the Dysfunctional Family is the level of violence and drama. If your family has members offing one another (usually for power), Honor-Related Abuse, incestuous relationships, alcoholism (and not usually of the Functional Addict variety), Abusive Parents, and habitual drug use, you're dealing with the former. If your family has a son that experiments with pot during a Very Special Episode, or a Lady Drunk mom who is a Functional Addict and does not harm herself or her family via her drinking, or the family just argues frequently, you're dealing with the latter.
Obviously, there is a time and a place for everything. If your show is leaning heavily towards the cynical end of the Sliding Scale of Idealism vs. Cynicism, it may be very appropriate to have a Big, Screwed-Up Family. If your show is a Deconstructive Parody of a more typical TV Dysfunctional Family, it may be appropriate to have that, too. On the other hand, if you wish to avoid Played for Drama and/or Black Comedy, it may be more appropriate to have a family that's just screwed up enough for a Screwball Comedy, but not violent or nasty. This can be very tricky. Generally, the way to avoid the family crossing over into "too dysfunctional" territory, is to make it clear that they do love each other, in spite of their many flaws.
Step Three: Where Do They Live?
As mentioned before, most Dom Com families are white, middle-class Americans. They usually live in a Big Fancy House (which usually follows Standardized Sitcom Housing construction a la 742 Evergreen Terrace. It is almost always located in Suburbia. But there's no rule that says it has to. You might have a family of Trailer Trash living in a trailer park. You might have an urban family. You might have a family that lives on a Farside Island with Bamboo Technology. Or a family that lives on the moon. You might have a family that is blatantly not of the Eagleland variety. They might live in Stepford Suburbia, or a Crapsaccharine World, particularly if it's a very cynical show.
Generally, people have neighbors, unless they really do live out in the middle of nowhere. So it stands to reason that your Dom Com family will have neighbors, too. What about them? Are they Cranky Neighbors? Or nice neighbors you only wished you lived next to. Do they compete over who has the nicer lawn? Are they Obnoxious In-Laws? Are they just like your main family, or do they exist as a Foil (i.e. The Smiths are a Dysfunctional Family and the Joneses are so perfect it hurts.) Is your neighbor a Funny Foreigner or a Cloud Cuckoolander? Or is someone going to fall for the Girl Next Door? Endless plotlines can be derived from neighbors and houseguests.
What About Extended Family?
Since the Nuclear Family is the norm in Eagleland (where much television originates), the focus will probably be on the main family. (Unless you do have extended family living with them, such as if they're from a culture where this is the norm, or taking care of a sick or disabled relative.) But, the extended family makes for good houseguests...and plotlines. For example, think of all that could happen during Thanksgiving dinner that might not happen during a "normal" dinner. Are there crazy cousins? Obnoxious In-Laws? Uncles prone to Lampshade Wearing? Aunts who qualify as Christmas Cake types, to the disappointment of other family members? A gay wedding being planned for Cousin Bob that Alice is uncomfortable with? Such a large extended family being invited to a family barbecue that the relatives qualify mostly as 24-Hour Party People? Holiday and other special occasion episodes are a good time to work with this.
- Remember that a Dom Com is a ''domestic'' comedy. Meaning that most plotlines should be close to home. There might be plotlines surrounding Bob at work, or Pastor Offeran at church, or Annie and Billy at school. It's OK to have a Vacation Episode, but do they really have to go on one Once an Episode?
- Since it is a comedy, be silly. Look at the Comedy Tropes index for ideas.
- While your family needn't be dysfunctional, remember that a family that's unbelievably perfect gets tiresome, and breaks the audience's Willing Suspension of Disbelief. If you can't stand the idea of a family that gets into a Cavemen Versus Astronauts Debate at the dinner table, try a Quirky Household. They're pleasant enough not to be dysfunctional, but (if played right) aren't so nauseatingly perfect. (Unless you're going for So Bad, It's Good using a family that Tastes Like Diabetes.)