NOPE not a brother of Hatsumomo(due to the hair), because she's an only child.
I'll name him Sumairu, and exaggerated translation of "Smile" in Japanese.
It's best to keep this guy's origins unknown(like where he lives and who are his family), but as inspired from one of my chats with my BF, he'll be one of the orphans.. BUT for a change, an antagonist to the group, the big bad bully from the orphanage.
After a long while that Jubei and the others are gone from the orphan, Sumairu had also escaped from the orphanage along with some of his crew that's on his league for bullying.
Sumairu had been causing havoc around Gongmen city, mainly bullying other kids and thievery.
Sumairu is a Nogitsune, a notorious& malevolent type of kitsune who doesn't serve Inari or the ten tailed kitsune.
There was something that had happened to his eyes along time ago, although it's clearly stated that Jubei did those out of revenge for the troubles he had caused her from the orphanage.
Currently, Sumairu hides his identity by becoming a friendly& approachable bookseller.. only lets out his benevolent side when he FEELS LIKE IT.
He has an interest for eyes that have rare colors not unlike hazel, red, green, or blue(which he finds boring).
When he's bored at night, he hangs around bars drinking and causing trouble.
His has two standard weapons; a katana& a hammer.
COLORS SOON COZ I'M SICK AS FUCK.
Sumairu (c) Me