"My older sister lives in Mexico."
Translation:Mi hermana mayor vive en México.
Why isn't the personal preposition 'a' used in this sentence? My answer was: A mi hermana mayor vive en Mexico?
The "personal a" is used before people who are direct objects. "My older sister" is the subject of this sentence.
Mi hermana es bonita. (subject)
Admiro a mi hermana. (direct object)
Another time you would see "a mi hermana" is if you have an indirect object pronoun to clarify:
A mi hermana le gusta leer. My sister likes to read.
Le doy mis libros a mi hermana. I'm giving my books to my sister.
I've really struggled to get my head round this use of personal 'a' and I think it causes most native English speakers a lot of problems because we don't have anything like it in English.
I've personally found marcy65browns explanations to be really helpful in understanding it.
Here's quick and dirty way of remembering when to use it. If you find a person or people at the end of a sentence with for example, my, he, their, her, the in front it's going to need that personal 'a'.
A few examples:
You call my sister - Llama a mi hermana
They defeat their enemies - Ellos derrotan a sus enimigos
She calls the police - Ella llama a la policia
He treats his employees well - Él trata bien a sus empleados
He calls his wife - El llama a su esposa