Alaikum salam sister.
A girl of your age is ready for marriage and capable enough to take responsibilities to manage a home and make the environment peaceful for its members, be it a single unit family or even an extended one. If your parents and siblings need you so much so that they cant survive then you can first start by convincing your partner of choice that you are able to help them as well as give time to his family and see if he able to compromise. If not then have insight in considering the proposal whether it is a right match or not regarding the fact that your parents will also be considered as his parents in future and he is somehow responsible for them at least through letting you help them.
If your parents are happy to get you married and settled which most parents would be for their daughter then know that they will somehow manage on their own. You can always pre-arrange a loan or a bank account for them that can help to run the house on a monthly basis and also keep in touch with them on a daily basis.
If you think its the right time and person for you then don't delay the marriage specially if you are ready for it and would fall in any forbidden act. InshAllah Allah will help you make the right decision.