Discuss tangled web weaver's answer to: Can I be held liable for sister's medical bills if she lives with me? She has no job and no insurance.

If she's a capable adult who just happens to live with you then of course you're not responsible for any bills she incurs, medical or otherwise. Are you her custodial guardian because she's an incapacitated adult or otherwise unable to care for herself? Even then you aren't personally responsible for her medical bills BUT if she's a minor and you are her custodial guardian then whether or not you must also pay her medical bills would is according to the terms agreed upon at the time the custodial arrangement was made.