If you’ve ever sat through a period drama wondering what everyone else is up to while the romantic leads dominate 90% of the screen time, then “Bridgerton” Season 3 Part 2 is for you.

It’s not that Penelope Featherington and Colin Bridgerton (or Polin, as the internet insists on calling them) don’t make an arresting couple. It’s just that we’ve known they were in the cards since day one. With a longer arc than either of the first two seasons’ pairings, their story leaves more room for others to breathe. This installment is stuffed with B-plot, and though it may be less aspirational than Daphne and the Duke’s erotic union, a lot of it’s far more relatable.

The first deliciously familiar moment comes in episode 5, when Eloise Bridgerton offloads to Cressida Cowper, her cynical replacement for her estranged best friend, Penelope, about Penelope. As Eloise finally draws breath, Cressida mentions that she’s “had a shock of my own,” actually. She confides she’s being betrothed to an extremely old man against her wishes.

“Lord Greer,” Eloise exclaims. “Is he not at death’s door?”

“Sadly, no,” Cressida replies.

Affecting a masterful handbrake turn, Eloise sits down and puts her hand on Cressida’s knee. “I would not have gone on and on had I known your plight,” she sighs.

It’s a perfect exchange. With so much of popular culture falling over itself to extol the exquisite power of female friendship, “Bridgerton’s” candy cane world is the last place one would expect a dash of realism. We know Eloise would rather talk about Penelope — or better, to Penelope — than Lord Greer, and we know Cressida knows she would. They are compromising, grudgingly, because the only thing worse than moaning to your second choice is moaning to no one at all. Their mutual dissatisfaction is a balm for anyone who’s felt the lack of an omnipresent WhatsApp group stuffed with people ready to go to brunch at a moment’s notice.

Messy platonic relationships are very much the season’s theme — fitting, considering the vacancy left by Colin and Penelope’s graduation from imperfect friends to imperfect spouses. Having hitherto been the picture of a supportive, empathetic, fun mom, Lady Violet, the Bridgerton matriarch, stumbles when met with an underwhelming romance between her third daughter, Francesca, and the monosyllabic Lord Stirling.

Violet’s struggle to accept that Francesca has fallen in love without any drama is redolent of mother hen types everywhere who need to be needed. There’s nothing duller than discovering one of your nearest and dearest is about to be lost to coupledom and hasn’t at any point asked your advice about it, or even had the decency to leave you with a scintillating account to chew over.

It’s another dimension of the bereavement Eloise feels at Colin and Penelope’s wedding breakfast. Welling up, she tells her other brother Benedict she’s simply shedding “tears at losing another friend to marriage.” No matter how much they love the newlyweds, watching them declare each other number one is never easy for those relegated to second place.

Thankfully, what is true of life needn’t always be true of “Bridgerton.” Violet’s absolutely correct in identifying the Francesca-Stirling relationship as the most boring in the series. And while Francesca makes the very fair (and true) point that “not every attachment must be dramatic and hard-fought,” that sort of thing makes for terrible TV. When Stirling’s cousin (now Francesca’s cousin-in-law) turns up in the last episode, Francesca, previously a chemistry vacuum, shares a look with her that’s almost as charged as the infamous Polin mirror scene. It’s not a massive leap to assume that Francesca’s married life has more excitement in store than her courtship.

In keeping with Season 3’s somewhat aromantic vibe, its most touching relationship isn’t between Penelope and Colin, but Penelope and her mother. Lady Featherington is the Kris Jenner of Regency Mayfair: cleverer than all but one of her daughters, and willing to do anything to secure their future — with or without their consent.

In Season 1, she’s a figure of fun, balancing the twin pressures of maintaining her daughters’ absurd wardrobes and her deadweight husband’s disinterest in finding them partners. Over time, she reveals herself as devious, ruthless and superficial, particularly regarding Penelope, who she habitually overlooks in favor of her sisters.

While the series’ attempt to paint Penelope’s Lady Whistledown column as a feminist outpost feels a bit forced, Lady Featherington’s belated appreciation of her daughter’s abilities is far more affecting. It’s the sort of evolution many of us wish our parents were capable of. Similarly, many parents might envy Penelope’s acknowledgment that many of the qualities that made her successful as Lady Whistledown — her ambition, drive and occasionally cut-throat attitude — were inherited from her mother.

“If we survive this round,” Lady Featherington tells her, “We must do better.” Leave it to a parent who’s made endless mistakes but is determined to try again to offer the most realistic, and most moving, expression of love.