This is an example of a multiple subject. In English, <em>a sentence can have one subject or multiple ones</em>.
<em>Example</em>: John is a very responsible student. (This is an example of a <em>single subject</em>.)
John and Ana are very intelligent students. (This is an example of a <em>multiple subject</em>.)
Other examples of multiple subjects include the following:
My sisters and I played together in childhood.
My dog, my cat, and my bird are the most beautiful animals in the world.
In a sentence, you can have the number of subjects you wish, always that then they are well conjugated; that is, they should be conjugated in the plural form of the verb because they are more than one subject.
