Should I Use Plural or Singular Pronouns?
Systems and individual alters have their preferences, so it’s always good to ask what pronouns they want you to use. The way things generally work, though, is that the whole system is plural – it is multiple alters, and so you would refer to them collectively with plural pronouns (they/them). However, when you refer to a single alter, you’re referring to a single person (he/him, she/her, etc.). This can get a little fuzzy with non-binary alters, who may use singular they/them pronouns. When in doubt, ask.
The main thing is not to be a jerk. If you get the feeling that the person fronting doesn’t want you to ask who they are, refrain from referring to them by pronouns, or use the pronouns for the host they may be masquerading as. However, if an alter tells you their pronouns, respect them.