GODDAMNIT DENNIS, STAY IN YOUR OWN CUT!
Oh wow I'm done. :y Well here's the finished product. It was a fun month!
The pixie's eyes: The tree in Uxie's eyes means Knowledge, the kanji in Azelf's eye means Willpower. Mesprit's iris is shattered into many different pieces representing the many different human emotions that constantly contradict one another, yet Mesprit is emotions personified, so imagine it being happy, sad, mad, angry, nervous, scared, and everything else ALL AT THE SAME TIME. I'd imagine if Mesprit existed IRL, it would seem like it's having a mental breakdown all the time.
The reason why they seem to be in a random order:
Articuno, Zapdos, and Moltres were befriended by Lugia, who is Ho-Oh's counterpart. Ho-Oh revived the crown beasts, and the crown beasts (especially suicune) seem to have a boner for Celebi because they shared TWO movies and a special together. Celebi was dubbed the New Mew by pokemon fans. Mewtwo is Mew's clone, and was born in Cinnabar. you can find Missingno off the coast of Cinnabar.
Latias and Latios have nothing to do with any other legendaries. Regirock, Ice, and Steel were created by Regigigas, who pulled the contintents together to form the current pokeworld. This created Heatran. Groudon and Kyogre then fought for dominance over the continential plates. Rayquaza is Groudon and Kyogre's trio master, and keeps the two in check. It shared a movie with Deoxys. Deoxys and Jirachi are related because stars and shit.
Cresselia is Darkrai's counterpart, and Darkrai shared a movie with Dialga and Palkia. Arceus created both of them, also the lake trio, all three of whom appear to be created for the sole purpose of sealing away Giratina and/or another member of the Creation Trio in case somebody (Cyrus) uses their powers for evil. Giratina is over there because it was banished from the real world and Sinnoh myths in general. It also shared a movie with Shaymin and they were the only two legendaries to have an alternate form at the time. Manaphione/Victini follow because Grass, Water, Fire. Also Shaymin, Manaphy, and Victini are all pixies.
Reshiram and Zekrom split from Kyurem, the original dragon pokemon. Zekrom and Thunderus are both electric type and both can only be caught in Pokemon White version. From then on it's kinda pure speculation for the relationship between the legendaries.