Dallas

 Sue Ellen and Pam start out mostly as polite strangers who are connected only because they marry the Ewing brothers, J.R. and Bobby, but over time they develop a complicated mix of rivalry, jealousy, and real affection as sisters‑in‑law. Their relationship keeps shifting with the family power struggles, affairs, and business wars around them, so they go from tense competitors to uneasy allies and sometimes genuine friends depending on what J.R., Cliff, and Bobby are doing at any given moment.