an IRL is another word for DA (delusional attachment). anyone can have an IRL and they usually arent permanent. people can have multiple IRLs ranging from just 1 to 50 (I have around 30-40). a person without DID or OSDD can be an IRL, so its not exactly a system term. but just because someone is an IRL doesnt mean they are any less valid then fictives
fictives are alters that are or are based off of fictional people or characters. fictives, while they already come from a media, can also have IRLs of different characters from different sources(but they dont have to)