Yujin and Nan

Finally! The Trustworthy and the Troublesome steeds of the mutant sisters.
Quick refresher:
Yujin (left)
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Name Meaning--> Embers
Friesian Stallion
The sweet and kind one
Venus' mount

Nan (right)
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Name Meaning--> Difficult
Andalusian Gelding
I mean his name IS Difficult. Although he has his moments, this boy needs an Experienced rider at all times
Mona Lisa's mount

Also, what are backgrounds?