I (16M) was told - not asked - by my father to teach my younger sister (15F). Earlier this school year, she was failing at multiple subjects: her grades were way below average, and extra classes weren't helping with the problem. Since I was the smarter one, my dad instantly assume that it is my job to help her for the final grade exam, which I'm not happy with in the first place.
Regardless, I decided to help her. But when I started to ask her about basic knowledge in her courses, I soon came into the realization that she has lost foundation across multiple subjects, mostly science-related subjects like Maths, Physic, Chemistry, and even Biology, which is her major (we are Asian). Not only that, she was very lazy: she barely did any homework or review, and somehow demands me to just tell her the answer so she could memorize it. In case if anyone was wondering if she could possibly have ADHD, she doesn't, and I know that because she was actually capable of learning hard courses, especially when she was capable of participating in extra math classes to take the entrance exam for her school (it is a gifted school). But the worst part is that my father allowed it to happen, simply because in his words, "she doesn't have time to start all over again".
I obviously didn't want that to happen. I don't want to write out the answers for her today just to get asked again when she has another test. And I have my own review and homework to do on top of that. We got into an argument, and she said I was suppose to help her and I'm "making everything complicated" and that "I could just say yes". In the end, I flat out refused to teach her. But at the same time, I feel confused, like I might have been too forceful on her, and also a bit of guilt on how it would have been my responsibility if she fails this upcoming exam.