Alpha sub?

Gay guy here. My husband is Dom top and I'm switch. Ideally when we play or are poly partnered I work as a sort of middle man - subbing for Dom while acting as Dom to third sub participant. However, sometimes I'm equal to Dom in my role over sub and sometimes I'm equal to sub in my role under Dom. I've seen the term Alpha sub and thought this might better describe my switch role within role play and scenes. However, based on the research I've done, Alpha sub seems to simply describe the most senior and experienced sub, who likely has some accompanying responsibilities, not really the switch role I fulfill. In terms of role play I think of warden/prison guard/prisoner as describing Dom, myself, and sub. Or perhaps, Daddy/older brother/younger brother. Is there a bdsm term that more accurately describes my middle role play position?