When two nouns or titles refer to just a single person or body, the verb should be? 

When two nouns having "and" between them represent a single body singular verb is to be used according to the rule of double-title concord. 

We can understand this using the following example:

Reema and Seema is interested in joining the art club. 

In the above sentence, nouns are two but present as a whole, "is " (A singular verb) is used instead to "are" ( a plural verb) which actually seems correct.