heyo;; i need some help with my boy justin

i'm sort of losing connection to him but I really do not want to trade him because it took me a while to get him back (gave them to my friend who then traded them; i was lucky enough that the person she traded him to wanted to give him away when they left the community and let me have him)
the main problem is that i can't figure out a solid personality for him. all of his siblings I've sort of got figured out and i'll give a quick run down
iro (twin bro) - very quiet and reserved; loves birds and does well academically
ash (nonbinary younger sibling [uses he/him pronouns often though]) - an ambivert; somedays very introverted and others very extroverted. if their friends jumped off a bridge they would too
julia (younger sister) - extremely loud and sometimes annoying. pulls off pranks the most and loves scaring her siblings
eliza (much younger sister) - the quietest and frankly most coldhearted of the kids; she does have empathy but definitely less than others
theodosia (much younger sister) - seen as warmhearted and the opposite of her twin sister, although they are kind of similar besides this. always wants to help others
and their parents;
dokuro (mom) - a quiet extrovert; loves to be around people just doesn't talk too much. adores kids (explains why she has six) and wants to foster some
finley (dad) - second loudest in the house right behind julia. not as into playing pranks but loves telling dad jokes and embarrassing his kids.
as you can tell i like to make some of them similar to each other but at the same time keep them different. i have no idea what direction I want to go with justin. i can never decide if I want him to be more introverted, extroverted, or an ambivert and thats usually what I build characters around. any help would be much appreciated c:
i have more kalons i need help with but i'll stick to just him for now
@Fearnoon - maybe he spent a lot of his time growing up bartering and trying to get the most bang for his buck?