I'm going to let you in on a secret. Professional wrestlers "Kane" and "The Undertaker" have been known as a tag team called "The Brothers of Destruction" but they are NOT brothers. I always liked the duo as a tag team and for so many matches, they were an intimidating duo.
With that in mind, I call your attention to this article that would have you believe that it makes sense for Kane to battle the Undertaker "one more time" as the respective ends of their in-ring performance years near the end. The article advocates for this because of their past as enemies, as shown in the first video below.
After considering the idea, I would actually advocate for Kane and the Undertaker to end their in-ring run as allies. Vividly, I can see the reunion of the "Brothers of Destruction" on the 1000th episode of Raw as they worked together to take down a bunch of other professional wrestlers. As far as the storyline goes, they are allies. The crowd responded enthusiastically to their appearance together.
Certainly, WWE is entitled to milk their history, but it should also be done with the idea that fans probably want to remember the duo as a powerhouse team than as enemies. It's not the same as other rivalries, such as Ric Flair and Sting. It worked for them to face each other on the last ever episode of WCW Nitro. The two had battled each other, off and on, for years and so seeing them battle in the final match on that show was fitting. WCW, for all of its booking missteps, actually made things right by showing the two hugging and showing respect for each other after their match.