//A small canon/headcanon post about Sara and her family:
Sara's relationship with her brothers is distant and strained, not unlike the relationship with her father. This is because she was taken in and adopted by the head of the Kujou Clan at the time, who already had two biological children of his own.
Kujou Takayuki, from the beginning, never saw Sara as his child. Sara was, first and foremost a child chosen by the shogun who would bring them prosperity. This in turn led him to believe that Sara was nothing more than a tool to be molded and shaped to serve both the clan, as well as the Raiden Shogun herself. This is a sentiment noted among some of the other characters in Inazuma, namely Ayato who has a line of dialogue about Sara that mentions her being a tool that Takayuki lost control of.
Sara underwent harsh training and treatment to mold her into the perfect tool and soldier, which led to most of the clan head's attention being on her instead of his own boys. This in turn led to resentment among her brothers, and is most likely the reason why Masahito is the most distant from Sara. That, and the fact that his father kept throwing Sara and her achievements in his face at the slightest hint of failure, even going so far as to threaten to have Sara replace him.
Masahito, in the end, remains distant from his adoptive sister, though he does talk about her from time to time.
Kamaji, on the other hand, has always been amicable toward Sara despite her being adopted. Out of both of her brothers, it is Kamaji that she would be the closest to, though she still keeps a respectable distance from him. Sara knows that she is not truly of their clan, and due to her status as an adopted child, as well as a youkai, she never will be.
Masahito is the eldest sibling and eldest son. Kamaji is the middle child and youngest son. Sara is the youngest child and only daughter.
tl;dr: Sara knows she is an outsider first and foremost, and while she does her best to treat her brothers as family, she can't help but remember that she's truly not one of them. Her adoptive father never saw her as one of his own, which led to much loneliness, while her elder brothers either keep her at arms length, or she keeps them as such.
