A simple sentence has a subject doing something. Only one thing happens in a simple sentence. Sometimes the simple sentence has a compound subject. In that sentence, two subjects are doing something together. Look at these examples of a simple sentence with a compound subject:
Bob and Mary came to the party.
The dog and the cat ran around the yard.
Mom and Dad took a trip.
In each of these sentences, two subjects are doing something together. These are simple sentences with a compound subject.
Sometimes a simple sentence has a compound subject – two subjects doing something together.
It’s your turn. Find the compound subject in this simple sentence: John and his brother rode their bikes. Did you figure out who is doing something? Good for you!