Board Thread:Theories and Speculation/@comment-1512913-20161125200227/@comment-1512913-20161128023220

Well, the Otsutsuki Clan members (aliens, not hybrid human descendants) like Kaguya, Momoshiki and Kinshiki, seem to have some sort of tradition in regards to chakra. Apparently:
 * they harvest a Shinju by continuously making more chakra fruits, until it and the planet with its inhabitants die out
 * the latest generation eventually absorbs the previous, like Momoshiki did to Kinshiki and like Kinshiki had done to his predecessors before, obtaining all of the predecessors' power

In my opinion, this is what Kaguya was expected to do too, to share the Earth's chakra fruit with other members of her clan, but she didn't. The databook states she wasn't the only one coming to Earth, but that she arrived with her clan. So most likely after she ate the chakra fruit all by herself, she either killed or absorbed the other Otsutsuki, some might have managed to run away.

So the original plan probably was supposed to go like this:
 * Kaguya and her clan arrive from space on Earth, Earth's chakra fruit is split among all of them (maybe Kaguya gets the biggest piece)
 * the planet's inhabitants are enslaved and more chakra fruits get forcefully produced
 * each new chakra fruit is split between the Otsutsuki, with the leader probably getting the biggest piece
 * this is done until the planet and its flora&fauna die out
 * when an Otsutsuki gets too old or is dying, his/her son/daughter or other kind of successor absorbs him/her

Kaguya probably didn't want to get absorbed by her successor so decided to eat the entire fruit for herself, getting all the Earth's chakra and becoming all powerful and immortal.

For Momoshiki's red Rinnegan, maybe.... Kaguya ate Earth's chakra fruit all by herself and got the Rinne Sharingan. The Sharingan and Rinnegan are the Rinne Sharingan split into two doujutsu, Sharingan being red and Rinnegan purple, but maybe the power doesn't always split the same way, so just like Momoshiki has red Rinnegan, there might be an Otsutsuki out there somewhere with purple Sharingan? Just a thought... just like a child has half his/her parent's genes, but even though a child is half of its parent, each child a parent has isn't an exact copy of its sibling despite each having the same percentage of genes from their parent, because there is randomization on the genes inherited...