'Bridgerton' introduced Lady Danbury's brother, but he's not in the books — here's what to know about Lord Marcus Anderson and his future on the show

• Season three of "Bridgerton" features Lady Danbury's brother, Lord Marcus Anderson.
• He won't be familiar to fans of the "Bridgerton" book series.
• Lord Anderson was created just for the TV show, but he'll probably be back in season four.

Warning: There are major spoilers ahead for season three of "Bridgerton."

Season three of "Bridgerton" delivers plenty of romance — not just for Colin Bridgerton and Penelope Featherington, but also for other members of the ton.

Season three premiered on Netflix in May and concluded on Thursday. Among the returning faces were a handful of new characters, including Lord Marcus Anderson (Daniel Francis), the brother of Lady Agatha Danbury (Adjoa Andoh).

Here's everything to know about Lord Anderson and his blossoming romance with another "Bridgerton" character, which seems likely to continue into season four.

Lord Marcus Anderson doesn't exist in Julia Quinn's 'Bridgerton' novels

In Quinn's romance novels, Lady Danbury doesn't have a brother. Like newcomer Lord Debling (Sam Phillips), Lord Anderson is an original character created specifically for the TV series.

When filming for season three began in 2022, Lord Anderson was described as "a charismatic presence who lights up any room he enters, attracting the notice of certain matriarchs in the town — and the ire of others."

Some fans suspected that he'd be a potential suitor for Penelope, but when promotional materials for season three were released, it became clear that his storyline would be intertwined with Lady Danbury and Lady Violet Bridgerton (Ruth Gemmell).

In one teaser, Lord Anderson and Lady Bridgerton were seen exchanging glances — with the matriarch biting her lip — as Lady Danbury observed with dissatisfaction.

Fans who watched the "Bridgerton" spinoff series "Queen Charlotte" will recall Violet telling Lady Danbury that she was considering opening herself up to romance again. So, it made sense that Violet's season three storyline would involve the possibility of love.

Lord Anderson and Lady Violet Bridgerton have a slow-burn flirtation in 'Bridgerton' season 3

Marcus and Violet first meet outside the Hawkins' Innovations Ball of 1815 during episode three, as he helps her pick her glove off the ground. Marcus approaches her later that night at the ball and Lady Danbury interrupts to reveal that he's her brother who's just visiting town. Even though Violet and Lady Danbury have been friends for years, Violet isn't aware that she has a brother.

Marcus isn't seen again until episode four, when he dines with Lady Danbury. When asked why he returned to London, Marcus says that his lack of company — and ladies — at his country estate brought him back to town.

Marcus and Violet talk at another ball, where he tells her that he hasn't been to Mayfair since the early days of marriage. When Marcus asks how she passes time in the city, Violet says that she and Lady Danbury enjoy meddling in the lives of the young people. She adds that Lady Danbury "molds society to her will." This is surprising to Marcus, who says that they're becoming "reacquainted," hinting at some tension between him and his sister.

As Marcus and Violet observe Francesca Bridgerton (Hannah Dodd) on the dance floor, they talk about their past relationships. Marcus says that his marriage wasn't a love match or even passionate at the onset, but he became fond of her and they were happy until her death.

Violet then mentions that she had a love match with her late husband, Edmund Bridgerton. In response, Marcus says he's envious, but hopeful of finding a love match in his "second act."

Lady Danbury leaves the party early but is stopped by Marcus, who asks her to put her molding skills to use in his quest for love. Lady Danbury dismisses him, saying that she's not interested in aiding his raking. But he claims he has pure intentions.

Season 3 ends on a promising note for Marcus and Violet

During season three, part two, Marcus pursues Violet as Lady Danbury tries to intervene and set him up with other eligible women in the ton. Lady Danbury's hostility toward her brother isn't explained until episode six, when it's revealed that he prevented her from escaping town and took away her chance at freedom the night before her wedding to Lord Danbury.

Lady Danbury and Marcus hash out their childhood grievance during episode seven, with Marcus explaining that he snitched on her to their father because he thought he was protecting her from the dangers of the outside world.

He said that he was always in awe of Lady Danbury's courage but was also afraid of her — hence why he never told her any of this before. Lady Danbury, in response, explains that her life has been so full of joy lately, and she was concerned that he'd take it away from her.

In the season three finale, Violet asks for Lady Danbury's blessing to see where her feelings for Marcus take her. Lady Danbury tells her that they're adults who are free to do as they please, but if the relationship sours, she's taking Violet's side over her brother's.

Violet and Marcus are then seen having their first dance together at the Dankworth-Finch ball as Lady Danbury smiles at them in support.

With a fourth season already in the works, showrunner Jess Brownell teased that fans haven't seen the last of Violet and Marcus' blossoming romance.

"I love that relationship," she told Entertainment Weekly. "I love what a slow burn it is. For Violet, who hasn't dipped her toes in the dating pool for so long, she needs a very slow burn."

Season three of "Bridgerton" is streaming on Netflix.