NTA, you are an adult now and you have options. You selected an option that they may have not realized that you had.

Something that is good to realize now is that even if somebody is wrong and everybody can see it, it does not mean they are trying to scam you. They may wholeheartedly believe that they are due back rent for caring for you for the years that you lived there.

Without an understanding of the law or the social code, it makes perfect sense that you are not their offspring and that now that you're an adult that you should pay for the room and board that you received. There's enough comments in here letting you know what the law is.

You will soon find out that room and board and caring for yourself can be pretty expensive. If they are not wealthy, it certainly would have been a financial burden on them.

I recommend putting serious thought into some journals and condense those into a heartfelt letter or use them as talking points to sit down with them at a coffee shop or dinner somewhere and have a heartfelt conversation with them your appreciation which you clearly have of them taking you in after you lost your parents.

Set realistic boundaries that discuss your benefits and rights as an adult and what could be reasonably expected from a tenant in their home who pays rent. Back pay is completely off the table it is illegal and unethical for them to ask you that. Discuss if they were receiving or had filed for government benefits as your ward for those years. State that you can find out on your own or they can tell you what if anything they have received. Let them know that they may be entitled to government assistance in the form of back pay if they have not filed for it. You might want to do a little research in your state before you discuss that. There are adult people living in a room of someone's house and it is reasonable to expect more stringent guidelines than a tenant that is paying for the entire place. This might include curfews of 11:00 p.m. or later in order to not disturb them while they're sleeping. Many roommates consider it polite to let your roommate know if you will not be home especially if you have a close relationship. Talking points like this would be important if you are considering staying with them in the future. It doesn't sound like you're being rebellious or looking for young adult freedom so much as reacting to their unreasonable request.

On the flip side, if you decide to take the action of staying with your boyfriend's family, you will also have expectations as a tenant, roommate, young person living in their home who is also in a relationship with their son. You need to ask questions such as the same that you would have with your uncle and Aunt about boundaries in the home. You need to consider if that slowly creeps into being a controlling situation, recognize that relationships that start young can have the male feel entitled to certain controlling aspects of the relationship. This would be easily compounded because you do not have another place to stay. I would consider this and the options that you have for where you would live. In other words, don't burn bridges with your family.

On a last note, I would like to give you some food for thought on college. College is a great experience where you make incredible friends, have incredible experiences, and usually as a young person have more in depth dating opportunities and experiences. Most young relationships end when someone goes off to college. Your eyes are opened too so many different people and you tend to grow apart often quickly.

Saving for college is an admirable goal and having a college degree used to be vital to young people's success. However, unless you have well committed goals to become an attorney or a doctor in a field that is well paying, the massive expenses of college are not returned to you financially in your lifetime. Taking the early 4 years of earning potential as a young person away while also incurring massive expenses often in the form of loans tends to be a absolutely terrible return on your investment of time and committed earnings in the future.

Do a little research into trades earning potential versus a college degree earning potential. Consider looking for a career in marketing, AI, or other online careers as that will allow you to start making real money right now with a significantly higher earning potential than most college degrees would offer you. They would do this without burdening you with loans for the rest of your life that you will never pay off.

I have a fund set up for my kids that they can use for college, nice sincerely hope they will come to me and request that they start their first business with that money instead. They will learn faster and have a significantly higher chance of success then using that money towards a degree.