There are loads of resources about creating great characters. But when it comes to creating great relationships--the perfect tag team, the favorite couple, the best friends--the writing world is lacking. Whether your characters are romantic partners, coworkers, best friends, siblings, or what have you, audiences eat up a wonderfully crafted duo, trio, or group.
People love Sherlock and Watson's relationship so much, that there is an entire fan community that roots for them to actually be together. Agents Mulder and Scully from The X-Files fit each other so well, they inspired the term "shipping." I was once watching Harry Potter with someone who turned to me and said, "You know, I love how Harry, Ron, and Hermione work so well as a trio."
Some kinds of relationships would still be entertaining to watch if the whole story revolved around the characters going to the grocery store--their relationship is that amusing. (In fact, one of my favorite X-Files episodes is where Mulder and Scully have to go undercover as a married couple living a normal life together. It's hilarious.)
So how do you create a tag team that readers can't get enough of? Well, here are some things to consider.