That would depend on a lot of variables. How did they get parentless? What is their living situation? What was their living situation before they became parentless? How old is this teen? And on and on and on.......
Well, this is my take on the general attitude and mindset of a teen who does not have parents, considering that I too am writing about something fairly similar. If the teenager finds him/herself without any familial support, I suspect the child would be the following: -Rebellious -Low self-esteem -Angry -Crude -Avoidant -Anti-social (not to be confused with the disorder) -Depressed -More prone to violence -Envious of other teens with parents -Unable to support own children (perhaps neglectful at best and homicidal at worst) -Awkward/withdrawn if placed in a social environment That's all I can think of right now. You should look up the Harlow Monkeys experiment for help since monkeys are quite close to humans and exude similar basic behaviour. The Harlow Monkeys experiment was conducted to see if contact comfort was enough for a monkey to be raised properly. The results are fascinating and would probably help you figure out how a teenager would act without any parental support.
From what I've seen, some are: prone to self-destructive behaviors more likely to become addicted to cigarettes, alcohol, pot more likely to neglect their academic studies surprisingly "people-oriented" with their friends, who become replacement families. Super attached and loyal to friends and girlfriends. Feelings of betrayal if a friend appears to abandon them. more willing to take risks and indulge in risky behaviors. some are VERY street smart, independent and territorial. They don't want anyone doing them any favors. Cynical about life and what it will bring to them. Willing to do things that are illegal/wrong if they see some immediate personal benefit. At least, I've seen this to be true about guys I've known in this situation. It depends on why they are without parents and what their resources are. rich or poor? guardian or no? Also, I once met a girl who lived in a homeless shelter because she was an orphan, and she was very quiet and withdrawn. Studious and hard-working, but barely spoke up. Kind of simmered with some kind of anger. Inability to form relationships or even work with other students in class. Always wanting to do "independent work" instead of group work. Intimidated by others. Hope this helps!
I think they'd kind of crave the parental experience so they'd seek family figures in others. If they have other relatives they'd look to them for it, otherwise perhaps in teachers or friends. I'm not sure they'd rebel because if they don't have parents and in your story this is something which allows them a lot of personal freedom what is there for them to rebel against? They might not have had rules and regulations forced on them. True people rebel for attention as well but I think for someone who has grown up without a close family they'd be more inclined to cherish the people around them rather than to tick them off with bad behaviour.
Okay then here's what I can give you from my perspective, hope it helps- They would have a very strong drive to survive that would allow them to push through things that most people can't even begin to fathom. I'm going to assume your character has been through a lot, so for the type of person I'm guessing you're writing about physical pain means next to nothing, emotional pain can be buttoned down. They cover their insecurities with humor and agression. They're the kind of person that prefers to be alone because nobody really understands anyway. They may have the view that everyone leaves anyway, so what would be the point in attempting to form a relationship. When they do form any type of relationship (friendship, romantic, have children) they may be intensely loyal. The kind of person who will do anything for the people who actually manage to get in the ring of confidence. They'll put their own wants and needs on holds indefinitely and even permanently if that's what the people they love need. They are broken in an unmendable way. Yet always retain hope. In short, they're probably the most contradictory person you'll ever write about. Good luck
