It's a long story. But before I start here is a little background about my best friend. He was never one to make friends. We were friends and had one other mutual friend in common but he never really made any long lasting friendships, apart from me, and always sort of acted better than everyone else. The latter, I think, was the main reason why people were put off by him. Another thing to note, despite being raised his entire life in the United States, he was born in South Africa. And, lastly, we both worked together.
Anyways, randomly one day at work, I made friends with this girl from Australia who was an intern and here as a student. She seemed cool, had an interesting story, and since she was new and it didn't really seem like she was fitting in well with others at work, I decided to include her into my group of friends. So, anytime we did anything or were just hanging out, I invited her to come along. She seemed to fit in well with my group and everyone got along, for the most part.
Obviously when there's a group of people, I can't talk to everyone at the same time so there were times when I would be talking to others in the group and not my best friend. As a result of this, somehow, he and the Australian girl started talking. There were things about the United States both of them hated, and he was more than happy to give her a willing ear (and I wouldn't because, while I admit the US has problems, most of the things she hated were trivial and the others just sounded like an outright hatred of the people of this country) while I shrugged them off. They bonded over that and, before too long, started dating. It was the beginning of the end of our friendship.
They would talk, nonstop, even when him and I were just doing our normal things together like we always had. At first it was fine but eventually it became too much. Despite that, never once did I discourage them or voice disagreement. When I found out she was going back to Australia, I had hope that since international phone calls were so expensive, it'd at least slow it down. Instead, he would spend hundreds of dollars on calling cards. Anytime I invited him anywhere, he'd be on the phone the whole time. And anytime I'd ask him anything, he'd ask her what she thought first. So, slowly, I gave up on him. I eventually quit my job but the death knell was him moving off to college. After a few weeks I realized that I was the only one making any effort and didn't want to be in a one-sided friendship anymore. I stopped, took a breather, and wrote him off.
That was over 10 years ago. He's tried a few times recently to reconnect but I've moved on. Just done with the whole thing.
TL;DR: Bros before hos isn't a real thing.