I have a pair of boy/girl twins who have always been in the same classroom. They are a source of support for each other even though they have their own friends. I had to request the same classroom for them prior to K (before tracking kicked in) and prior to 5th grade (break-up of GT class due to Common Core). During 1st through 4th, they were in the stand-alone gifted classroom, but even then the teachers verified with me that I was okay with them being in the same classroom. In your case, I would lean towards demanding (politely but firmly) that your DS be transfered to his twin's class for the sake of his own emotional health as well as the family's peace and convenience.
