The significance of 7 and 13?

The climactic battle in Kingdom Hearts III will be between Seven Guardians of Light and Thirteen Seekers of Darkness.
Just after finishing Dream Drop Distance for the first time, I wondered if those two numbers together boasted any sort of significance that I wasn't aware of.

As time went on, the interested faded a bit. But with the recent announcement that Digimon Story: Cyber Sleuth would be released outside of Japan for the PS4, something once again sparked my interest.

I looked up some information on Cyber Sleuth because I was interested, and in the process, I learned quite a bit about some Digimon lore that I had little knowledge of. Specifically, the Royal Knights and the Demon Lords.

The thirteen Royal Knights have typically been depicted as antagonists throughout the Digimon series, more often coming into conflict with the protagonists rather than trying to help them, but they are all regarded as Exalted Digimon and were assembled to keep the peace of the Digital World.

On the other end of the spectrum reside the Seven Demon Lords, each of them very sinister or demonic in appearance and representative of one of the Seven Deadly Sins (Greed, Sloth, Lust, Pride, Envy, Wrath, and Gluttony). They've also come into conflict with the heroes of the Digimon franchise over the years, but are more obviously villains than the Royal Knights have seemed to be.

Here's what I find interesting: Kingdom Hearts is now setting up to have a struggle between Seven Lights and Thirteen Darknesses. Digimon, however, has seen a struggle between Seven Darknesses and Thirteen Lights, the former of which are suggested by the Seven Deadly Sins, and thus have a theme. This complete reversal is quite a conundrum and makes me very curious as to what, if any, significance there is to the numbers 7 and 13 used together.

What does this say about the Seven Guardians of Light? Do they represent the Seven Deadly Sins as well? (̶I̶f̶ ̶s̶o̶,̶ ̶L̶e̶a̶ ̶i̶s̶ ̶d̶e̶f̶i̶n̶i̶t̶e̶l̶y̶ ̶g̶l̶u̶t̶t̶o̶n̶y̶ ̶a̶f̶t̶e̶r̶ ̶a̶l̶l̶ ̶t̶h̶a̶t̶ ̶i̶c̶e̶ ̶c̶r̶e̶a̶m̶.̶ ̶X̶D̶)̶

Or perhaps they could mean some opposite of that, such as the Seven Archangels or the Seven Virtues.

 

Lucky vs unlucky ? Does anyone here expect the seven lights to lose in the end ?

Not sure why seven is considered lucky but it is.

I do know why thirteen is considered bad luck though (in spite of what the national lottery would have you believe): during his last supper Jesus has twelve guests at his table. The twelfth apostle, therefore the thirteenth person at the table, was Judas. The traitor. Considering Xehanort' s keyblade bears a goat emblem I wouldn' t be surprised to find more of those "subtle" Christian symbols.

 

Oh right. "And God blessed the seventh day, and sanctified it."
Wasn' t Roxas the traitor the thirteenth member of the organization btw ?

 

The first to be regarded as a traitor was Marluxia.

 

I guess Axel could qualify as a traitor as well, but Roxas is the only one who actually hindered Xemnas' plans.

 

Normally number 7 is considered a lucky number , although sometimes it can be considered unlucky, 13 is considered unlucky and has been considered lucky to some
I also believe that both numbers can be used in a variety of religious references
Also I think that I read somewhere that both number 7 and 13 are both numbers that represent death in some way ( I think both may represent life as well but not sure about this) I think that number 7 does at least not sure about 13 though

Although the number 7 and 13 also do seem to be used a lot in the series
Organization 13, kingdom hearts 13 word title, 13 floors castle oblivion, 7 Princess of hearts, 7 lights, 13 seekers of darkness.

The ones that I would consider to of betrayed the organization is Marluxia, Larxene, Axel and Roxas , although couldn't it be said that Saix was going to be one at one point

 

As stated above, it's lucky versus unlucky. Seven against thirteen is basically like light versus dark (another strong theme in Kingdom Hearts), or good versus bad (ditto). It's just another way to place a dividing line between who you want to win and who you want to lose.
It's often a ploy of screen writers, authors and poets to put a reversal on the roles you find an object or character traditionally playing. A good example is Paradise Lost by John Milton. Instead of taking the side of God, he projects the story from Lucifer's point of view (it's actually quite good with footnotes).

It also depends on the predominant culture, superstitions and religions of the area that the story, movie or TV show is created. Superstition with the number 13 probably started with the Mayans, who believed that number would lead to the apocalypse. After that, monks who were in charge of creating calenders and marking festival days would have a harder time if the year held 13 full moons instead of only 12, so they named it as unlucky.
Old cultures that celebrated femininity and worshiped the moon considered 13 to be feminine symbol because of the lunar symbols, thus one of good luck. Most Italians also consider 13 to be lucky and 17 to be unlucky.

Myself, I've always found it ironic that Organization 13 had thirteen members, while Jesus and his twelve apostles make up 13.
With that in mind, technically they made Xemnas into Jesus.