This is a head canon that Kagami and Xanxus are related to explain the eyebrow thing. This one is where Kagami is Xanxus's father. For the sake of convenience lets call Xanxaus's mother Mary.
Kagami married Xanxus's mother, Mary. A beautiful lady who was at Japan sight-seeing during Kagami's last year there. After they got married they moved back to her home country, Italy. After while he was invited to play basketball with his friends from high school. Mary didn't go with him because she was pregnant. He only went because she said she was going to be alright.
During his time in Japan, the agreed upon meeting place, he had fun with his friends and gushed about his wife and unborn son. But tragically during the flight back, his plane crashed./p
Three weeks later and the wreckage was found in the bottom of the sea. A total of 100 people had died. No one survived. They had only found out who had died from the plane's attendance of who had gotten on with a ticket.
After she went to the funeral, two months pregnant, she spent four months in Japan with a kind friend of Kagami's, Akashi Seijuurou. Once she felt comfortable with returning to the house filled with memories of him. Once she returned to Italy she found her house had been burned down including a few other's due to faulty wiring. With the little money her husband had left her she was able to afford a house in the slums and a relatively clean place to give birth to a healthy baby boy named Xanxus.
Three weeks after giving birth to him the full effects of her husbands death hit her hard. With no working family member to rely on she had no source of income. No source of income = No money. No money = No house. No house = No son.
Shortly after these thoughts began she lost her sanity. But somehow got a poor-paying job at a factory. Life continued for the two. The-crazy-lady-and-the-boy is what they were called. When Xanxus got older his features became more prominent, dark black hair from his mother, red eyes from his father, as well as his double eyebrows.
When Xanxus began to produce sky flames his mother didn't care much. As long as he didn't go burning down no houses. But once she heard that someone who could make the same flames was in town she wasted no time in introducing her son to the man and convincing him he was the child's father.
She knew he wasn't Xanxus's real father, she could never forget the man with red hair and eyes. Besides, she only just meet the man today. It seemed to others who knew her that she regained her sanity for just a moment. All that was going threw her mind at the time was, "Can he provide a safer home for Xanxus? Can he take care of him?" and not much else.
You know, this was supposed to be short, and sweet, and cute. Not long, kinda boring, and a bit sad. Please note that Kagami is/was in his mid 30's when he died. I hope you enjoyed reading this and will review.