Hi Tinah,
I is the first person singular English subject pronoun. When another part is added to that subject, it doesn’t change case and become an object pronoun. If you say I want to walk to school, you also say My sister and I want to walk to school.
Me is the object pronoun, so it receives the action of the verb. It also does not change when another part is added: My mom drives (my sister and) me to school.