"Where is" versus "where are"

Is it correct to use is rather than are in this question?

Where is my mother and father?

Grammatically, it should be where are my mother and father? but, for some strange reason, I think I would use where is my mother and father? and I can't explain why that is. Perhaps, I used this structure before while growing up, without knowing all of the grammar "rules"; if there is an explanation for it, that would be great.

Solution 1:

There are many cases in language where the form that sounds natural isn't necessarily the form that you'd "logically" expect, according to a specific type of logic (that you might apply in mathematics but which isn't necessarily the logic upon which language works).

At least three factors could be at play for why Where is my mother and father? (or at least Where's my mum and dad?) sounds more natural than with "are":

• in general, there's a tendency to use "is" instead of "are" with a plural subject in informal usage especially in certain set expressions such as there's..., it's...
• in some cases there's a tendency for elements near to each other to "leak" onto one another even though if you analyse the structure of the sentence you wouldn't expect it-- there are all sorts of cases of this in different languages, some of which have become more or less acceptable even in careful usage (in languages with agreement between adjective and noun, you get cases e.g. of two nouns with differing genders modified by the same adjective, and the adjective may just take the gender of the noun that's nearest to the adjective, rather than a combined gender).
• your "mind" may just be treating mum and dad as a singular item (another example to consider: "My mum and dad is what's important to me").

Solution 2:

Because your father and mother cannot be the same person, you should use are (the plural form be).

In general, the form of predicate is decided by the subject of the sentence in a question (and in every kind of sentences as well).

The only special point of some questions is that the structure of the sentence is (at least partially) in reverse order.

Take your question as an example,

Where are my mother and father?

where are comes before my father and mother, while in a declarative sentence, it is

My father and mother are at home.