Let’s look at three modern masters of the family drama:
Bad family drama has characters saying exactly what they feel ("I hate you because you were mother's favorite!"). Great family drama weaponizes subtext.
The Chekhov’s Gun of Family Secrets If you hang a secret on the wall in act one (e.g., "Grandma never talks about her sister"), you must fire it by act three. Secrets are the physical currency of family drama. The longer a secret is kept, the more devastating its release.
The Ghost of Conversations Past Family dialogue is not original. It is referential. Every argument a family has today is actually a reenactment of an argument from ten years ago.
The Silent Treatment as Plot In complex relationships, what isn't said is louder than what is. A week of silence between spouses. A father who never says "I love you." A daughter who refuses to visit the grave. These silences are turning points. Write them as physically as you write screams.
This spans decades or centuries. Think One Hundred Years of Solitude, The Godfather, or Pachinko.