My little sisters are my most avid readers, but it took some time for names to stick, so Kassia was "big sister" or "blue girl" and Nora was "little sister" or "short hair girl" for a while. Luisa is "blond girl".
Every male character with lines so far has been called "hot guy", but now that there are three of them, my sisters had to get creative and give them their own names, so: Den is "big bro", Beyren is "the hot ponytail guy", and Caen is "man bun"... lol
Straightforward enough :')