With this setting, wouldn't there be very loving conversations? They really love each other, right? They're not just some old brother-sister thing! This is not some bloody Mary Sue harem, ah, have you been discovered yet [laughs]
Before the genocide.
"I want to be my brother's bride"
"No, my brother is mine too, and I also want to be his bride."
"Sasuke is a boy and cannot be his brother's bride."
"Wouldn't the boy be at a disadvantage?"
"Let's see, Sasuke will be my brother's groom. Hey, you have to thank me for my magnanimity."
"Who wants to thank you? My brother is mine too."
"..." Embarrassed, when Uncle Itachi heard this conversation, he silently looked at his younger brother and sister, each holding one of his thighs, and cried silently in his heart.
After genocide.
"Xiong Kong, what is your dream?"
"Recover the Uchiha clan, become the greatest ninja in the ninja world, step on the tailed beasts, and roam the eight major ninja villages..."
"What a... Big dream."
"Then..."
"Then?"
"Being my brother's bride~~"
"...."
——
The setting CP is not Mr. Itachi... Anyway, it is a story about a Uchiha brat who turns black, becomes tsundere, and mutates, acting coquettishly and acting cute.