As we know Brandon and Ritchie are brothers in this roleplay. I'm going to say they are twins for convenience( Brandon is older by an hour).
Though they are brothers they don't have the same master and Ritchie mentioned that we was raised by his master to kill demons. Why is th is?
I believe that the parents didn't know they were having twins and when the twins were born the parents left Ritchie in the forest.
Ritchie's master found him on his walk surrounded by the demons and killed them all. The master then decided to raise Ritchie as his own.
Brandon on the other hand was raised by the parents till he as 5. When he turned 5 he was placed to live with his master because he showed interest in becoming a demon slayer and was mad at the parents( the parents would've been able to visit Brandon wished).
Why was he mad at the parents? He found out he had a twin from his aunt. Brandon and Ritchie when growing up always felt something missing and would both have dreams were they interacted with eachother. They at first thought it was an imaginary friend they made up to keep them company when sleeping.
This lead to Brandon asking the parents about his dreams, but they never gave him an answer, just telling him to ignore the dreams/feeling or they changed the subject. The aunt was the only one to tell him the truth.
Ritchie and Brandon know they were brother because their masters did some investigation. What lead to them investigating was when they first met. When the twin first looked eyes they and spoked in words the masters couldn't understand stand. When they asked their apprentices about it they didn't understand how they knew it either and they both mention having the same dreams of the other.
Brandon was the first to mention the twin thing the aunt told him about and how this whole family thought him to be dead from being left in the forest.
This lead to the twins taking some sort of test that came back positive of being related. After that the masters found this out they let Brandon and Ritchie spend time together. Over the years they would take turns visiting each others place of residence. They would still follow the training plan their own masters set( Ritchie's become a little more relaxed when visiting Brandon) and at the end of the day they would sleep cuddled up with each other.
