Answer:
Ximena y Alicia conocen a mi hermano mayor, José.
Step-by-step explanation:
"Ximena y Alicia conocen a mi hermano mayor, José" is the sentence that is grammatically correct because the correct verb to use is "conocer" (not "saber") and "conocen" is the correct conjugation, which is the third person plural form of the present tense (ellas, Ximena and Alicia).