Final answer:
In English grammar, when a compound subject is connected by 'or' or 'nor', the verb should agree with the part of the subject nearest to it; thus the correct form is 'Either my parents or my brother is the culprit.'
Step-by-step explanation:
The statement 'Either my parents or my brother is/are the culprit' raises a question about subject-verb agreement in English grammar. The correct verb form to use in this case depends on the subject closest to the verb. When a compound subject is connected by 'or' or 'nor', the verb should agree with the part of the subject nearest to it. Since 'my brother' is the singular subject closest to the verb, the singular verb 'is' should be used: 'Either my parents or my brother is the culprit.'
The statement "Either my parents or my brother is the culprit" underscores the importance of subject-verb agreement in English grammar. When a compound subject is linked by "or" or "nor," the verb aligns with the element of the subject closest to it. In this instance, the singular subject "my brother" is in proximity to the verb, and, therefore, the singular verb "is" is the correct choice.
This grammatical principle ensures clarity and precision in conveying the intended meaning. While the compound subject involves both parents and a brother, the use of "or" indicates a singular entity is the culprit, necessitating the singular verb form. This rule of subject-verb agreement is a foundational aspect of English grammar, contributing to grammatical coherence and effective communication.