River Guardians

I think it's in the Materials Collection where it says these two are twins, but they are from different planets if I read the manga right. Do you think it's possible for their Sailor Crystals to be "twin" crystals without them actually being biological sisters?

Anyway, for the sake of avoiding incest I've made them very sisterly here! I meant to make Lethe on the left but then I forgot

Other Sailor Legs:
Let's Play - Mars & Venus
Come Get Me - Uranus & Neptune
Another Use for This - Mercury & Jupiter
Friends with Benefits - Chibimoon & Saturn
For You, Anytime - Moon & Pluto
Am I Not Good Enough? - Moon & Fighter
Making Up - Moon & Mars
Star Crossed - Cosmos & Galaxia
Parallel Pals - Kousagi & Chibichibi
Venus Love Chain Encircle - Venus & Healer
Making Thunder - Jupiter & Maker
Shocking Love and Beauty - Venus & Jupiter