This is the second in an occasional series about TV series and episodes.

Twenty-five years ago today, we were introduced to the Reed sisters.

There was headstrong Teddy, the alcoholic divorcee who was as idealistic as she was cynical. There was socialite Alex, whose materialism and self-absorption made her an easy butt of jokes. There was naive younger sister Frankie, whose junior role and lack of years made her vulnerable and in need of her sisters’ protection. And there was Georgie, the down-to-earth and level-headed housewife who functioned as a den mother, keeping these neurotic characters in check.

“Sisters,” the series that chronicled their navigations through their 30s and 40s amid divorces, affairs, children, illness, deaths, and addictions, ran for six seasons over the span of five years. In many ways, the show was a precursor to “Brothers & Sisters.” Not only did both series show the highs and lows of sibling dynamics, both series began with the aftermath of the father dying. In both shows, the characters learned their late father had cheated on their mother and they might have another sister. In “Sisters,” that was Charlotte, who replaced Frankie when Julianne Phillips left the series. In “Brothers & Sisters,” the potential half-sibling was future “Revenge” star Emily VanCamp.

But beyond that, “Sisters” is part of a stronger TV lineage: the female quartet, a topic I’ve also written about here and here. Centering a show around the lives of four women exploring sex, relationships, family, and aging is a popular trope now, as we’ve seen it on “Living Single,” “Sex And The City,” “Desperate Housewives,” “Hot In Cleveland” and on the current HBO series, “Girls.” The prototype of this, of course, was “The Golden Girls,” in which Estelle Getty, Bea Arthur, Rue McClanahan, and Betty White developed the archetypes that Patricia Kalember, Sela Ward, Swoosie Kurtz, and Phillips would respectively play in “Sisters.”

As numerous are the examples of this structure are now, “Sisters” premiered at a time when the only other shows to focus on four distinct but strong women were “The Golden Girls” and CBS’ “Designing Women.” The latter was an important evolution from “The Golden Girls” to “Sisters,” as the women on “Designing Women” were not older retirees, but women still working and raising families. “Sisters” expanded on that possibility by giving the women the shared histories of sisterhood, and turning the series into an hourlong drama. That more serious lens allowed the show to tackle some of the pressing social issues of the early-to-mid ’90s: George Clooney’s smoldering hotness, HIV, AIDS, surrogate mothers, and same-sex partnerships. In many ways, “Sisters” was ahead of its time, as it addressed topics that society is only now able to begin to articulate. Alex’s discovery that her husband enjoyed wearing women’s clothing sparked a discussion on the show about what it meant to be masculine or feminine. With the 20/20 hindsight of 2016, some of those scenes might seem dated or borderline cringeworthy now that we have more awareness and sensitivity toward gender identity. But the show certainly didn’t treat the dynamics of gender identity as a cheap, throw-away joke, giving it some nuanced attention that many shows are only beginning to address now. The brazen, sometimes crass ways that the women on “Sex And The City” or “Girls” have discussed sex and sexuality owes much to the spa scenes of the early “Sisters” seasons, during which the four Reed sisters would be shown in towels in a sauna, discussing everything from their families to their sex lives. A controversial line about multiple orgasms was ultimately cut by the network, but there were many lines and scenes that remained.

“Desperate Housewives” built upon the foundation laid by “Sisters,” transporting the four archetypes from the distinct Winnetka, Ill., into the vague, could-be-anywhere Wisteria Lane of fictitious, region-agnostic Fairview. The struggles of raising a family and keeping up appearances in a suburban setting, which at most had been a subplot in “Sisters,” became of the main focus of Marc Cherry’s hourlong “Desperate Housewives,” in which a spacey divorcee, a self-obsessed fashion model, a harried business exec, and dutiful housewife all struggle with divorces, deaths, affairs, families, and aging while leaning on each other, often in the form of flashbacks to their younger selves. Sound familier?

But for all the familiarities among these shows, each one put its own spin on the characters and the group dynamics. And the concept did cross into at least two shows focusing on four men: Mark Wahlberg’s “Entourage” and “Noah’s Arc,” which focused on four gay men of color living in Los Angeles.

Perhaps it was the Saturday night time slot, or the fact that “Sisters” didn’t make it onto DVD until about a year ago, but the show seems forgotten compared to the other shows we’ve mentioned. The increase in the number of digital TV services will hopefully mean that we can one day stream “Sisters” so that we can check in on Teddy, Georgie, Alex, and Frankie as casually as we can Dorothy, Sophia, Blanche, Rose, Carrie, Charlotte, Miranda, Samantha, Bree, Susan, Lynette, and Gaby.