#fraternization

I maybe went a little too in-depth into the research/re-reading to answer this question, but in my defense, it's a good question and I love rereading our own writing. :)

Raidou sets out the fraternization rule in Take the Mask: "No ANBU agent is permitted to fraternize with a senior officer. Same-rank liaisons are allowed but not encouraged, particularly within your own team." But he admits in Eight Hundred Eyes Are Better Than One that it's an unwritten rule, "intended primarily to protect rookies," and there's certainly no rule against fraternization between officers.

Dropping further back: in Heaven's Got a Plan For You, when Raidou confessed to Minato and Sagara that he'd had a one-night stand with Ryouma six months before Ryouma was assigned to his team, Raidou was a lot more concerned about that potential issue than either Minato or Sagara were. Partly, of course, because he's the one who'd have to deal with it; probably also because he'd seen Ryouma's potential emotional instability, and they hadn't! But I think for both Minato and Sagara, their primary concern is the smooth functioning of the team and the accomplishment of the mission. As long as those aspects aren't impaired, whatever the team members do in their private life is their business. And so the only important question for Raidou, as a captain, is whether he can set the appropriate boundaries that he himself thinks are important to successfully lead his team.

Given all of that, and given that a captain and a lieutenant must necessarily work together more closely and rely on each other much more than a captain and his newest rookie, I suspect Minato would be not at all surprised to learn that any particular set of differently ranked officers in the same team was fucking/dating/planning their wedding. Fraternization is only a problem if it actually causes a problem.

As for whether he noticed anything between Genma and Raidou when they visited the Palace, as Kurenai suggested in You Have That Effect on Me, I think Kurenai probably was biased by her assumptions at that point. As Raidou points out, he and Genma behaved in a perfectly professional manner while visiting the Hokage's apartments, and there was nothing for Minato to notice. Minato's suspicions really were only (mildly) activated by encountering the threesome at the festival.

(His thought process probably went something like: Huh, Yuuhi? Wouldn't have expected that. They seem to know what they're doing. All right, let's get Naruto out of Shiranui's hair...)

jon had no idea any of this was pre-planned when he and ariana were going through grindr profiles. she just so happened to really like cameron and kept prodding him to send a message until he relented. words were exchanged and a meeting was arranged. now, cavanaugh stood outside the door of the frat house and the door’s just opened. apparently, the frat boy’s ‘need for dick’ was too strong (or annoying) for ariana to handle. so, why not go to someone who specialized in giving dick?

“jon mahoney?”

As long as they’re both officers or both enlisted, and as long as they are not in a position where their relationship could compromise the mission or one’s ability to carry out one’s duties, inter-service romances aren’t typically seen as a problem.

Polygamous relationships depend on military law. With the UCMJ, the Uniform Code of Military Justice which covers the United States Armed Forces, bigamy is specifically prosecuted under Article 134, the catch-all for anything contrary “to good order and discipline” which covers offenses like dueling or bribery. 

Having kids with multiple partners might run afoul of Article 134 for extra-marital sexual conduct (or adultery if one of them is married to someone else). The soldier might be seen as acting contrary to good order and discipline or irresponsible behavior. But plenty of soldiers have had children with a partner whom they later divorced (divorce is rampant particularly among junior enlisted) and had another spouse with whom they have had children with no problems as long as all childcare responsibilities are met.

Thanks for the question, Anon.

"Women, broads, dames, beetles, girls, skirts, frails, molls, babe, frauleins, Mademoiselles: That's what the boys wanted," Webster wrote. 

He went on to describe the results: "The cooks were keeping mistresses; the platoon lovers were patronizing the barn; McCreary had a married woman in town; Reese installed his in a private house; Carson fed an educated, beautiful, sophisticated Polish blond (whom he later married); the platoon staff visited a D.P. camp nightly; and in Zell am See, home of the most beautiful women in Europe, the lads with the sunburned blondes were fulfilling their dreams

—after talking about women for three years, they now had all they could want. 

It was the complete failure of the non-fraternization policy." For those who had wanted and could afford them, there had been women in London, Paris, along the Ruhr, but, Webster observed, "in Austria, where the women were cleaner, fairer, better built, and more willing than in any other part of Europe, the G.I.s had their field day."

One of the heartbreaking things in TLJ was when Poe told Finn to turn back and said "that's an order." It broke my heart bc you can't have a relationship like that. It felt like the book closing on Finn/Poe, and I didn't really see it addressed in fanfic, either. It just made me sad.