[This content is out of date and no longer canon (This ship is no longer canon)]
Following the events of ORAS, Wally decided to hone his skills as a trainer so he wouldn’t keep lagging behind May. He ended up spending a lot more with Brendan as a result, often asking the other boy to help him train or offer advice. Over time, Brendan began to develop feelings for the sweet and determined Wally, but was always too embarrassed to confess, despite May’s continual encouragement. Eventually, Wally and May both get jobs at the Hoenn Battle Frontier as Frontier Brains, which is where Wally first meets Anabel. The two hit it off and eventually start dating, much to Brendan’s chagrin.
While he knows he should move on, he can’t help but want to still spend time with Wally and has a bad case of pining. He’ll go visit the Battle Frontier and just stare wistfully, but feels like he can’t hang out with Wally anymore since he’s afraid he’ll end up spilling his feelings and making Wally feel bad. He just doesn’t know what to do. May eventually gets fed up with the situation and tells Wally and Anabel why Brendan is always hanging around. The couple end up having a discussion about how to best talk to Brendan about the situation, since even his best friend May can’t seem to help. It’s at this point that Wally confesses that he too had feelings for Brendan but had been afraid to confess, not that it changes how much he loves Anabel of course!
After these revelations, Anabel ends up thinking a lot about the situation. She loves Wally, but she hates to see him upset and torn about this situation. She probably would have been mad at Brendan if he had been trying to ‘win Wally back from her’ or something, but he’s clearly doing his best to respect their relationship despite his feelings, which she finds pretty admirable. Plenty of others wouldn’t be so courteous. And now that she thinks more about it… Brendan is a strong trainer, smart, she’s heard nothing but good things about him from Wally and May, and he’s not bad looking to top it all off. If Wally and Brendan really do still have feelings for each other (on top of Wally’s feelings for her), then why can’t they solve the whole problem by just all dating each other?
She proposes this solution to Wally who is a bit surprised at the idea, but they agree to ask Brendan if he would be okay trying out this kind of relationship. Brendan is just shocked that he’s even getting this chance and agrees. Over time, they find that this dynamic really works for them. They all love each other and are all happy with their relationship. Wally eventually retires from his Frontier Brain position to take over the Petalburg Gym from Norman, while Brendan becomes a professor like his father. Between three busy jobs and the four children they end up having, there’s certainly never a dull moment in their household, but they wouldn’t have it any other way.
May, meanwhile, likes to smugly take credit for facilitating all of this.