The Expanse appears to have dodged a potential bullet by omitting a book romance angle from season 5. In The Expanse's latest run on Amazon Prime, the 4 core characters are split, sent on separate missions during a much-needed break from saving the world. Amos Burton returns to his home city of Baltimore on Earth, where he reconnects with the ghosts of his past after learning a loved one has passed away.
Amos' backstory in the opening 3 episodes of The Expanse season 5 incorporates elements of Nemesis Games and a novella called The Churn, which sits alongside the main series. As in the source material, Amos meets Charles, the widowed husband of Lydia, whose death prompted Amos' return. The Expanse reveals Amos' real name is Timothy, and when he was a child, Lydia acted as a mother figure to him, pulling the youngster out of bloody street fights and encouraging "Timothy" to be his own man by resisting his violent impulses. The episode shows flashbacks of Lydia mothering a young Timothy, and Charles reveals how she always hoped her adopted child would return to Earth before she died.
Unlike the books, however, The Expanse season 5 doesn't give any suggestion whatsoever that Timothy and Lydia became sexually involved when the boy grew older. In fact, the episode seems to deliberately play up Lydia's maternal role in Timothy's life, so as to move as far away from a romantic relationship as possible. In the original book series, Lydia fostered Timothy from a fellow prostitute, and as the child grew older, he joined the same crime Baltimore crime syndicate. The pair began having sex, but weren't what most would consider "in a relationship." This is a more extreme example of the different societal standards in The Expanse, which also includes group marriage and open polyamory.
While The Expanse season 5 leaves out this element of Amos' past during the Baltimore backstory, his unusual sexual awakening could still be revealed in a future episode, although Lydia's portrayal in live-action makes this very unlikely. The age difference between Lydia and Timothy in the flashback scenes is very pronounced, and her caring actions give the impression of a mother even before the audience learn who she is. Were The Expanse to go back and make their relationship sexual, the story would become very uncomfortable indeed.
The apparent omission of Lydia's romance with Amos is a certainly a wise one. Although the two aren't biologically related, the fact Lydia raised Amos virtually since birth makes their affair in later years just a little bit creepy. The Expanse might get away with this angle in the books, where the reader can't visually see the characters, but it's a far tougher sell for live-action, where it would be impossible to paint the relationship as anything other than an abuse of Lydia's parental role. Amos' story doesn't lose anything by making Lydia purely a foster mother, and The Expanse saves itself a heap of potential controversy by not taking this route. The Expanse is often described as "Game of Thrones in space," but this sort of illicit tryst is perhaps something the Amazon series doesn't want to borrow from George R.R. Martin's playbook.