An older, barefoot boy is talking to a younger, shirtless boy in flip flips in the middle of the street.
Two boys are talking in the middle of a street.
The first sentence states that an older boy is talking to a younger boy in the middle of the street. That would indicate that two boys are talking in the middle of a street.
An older boy and a younger boy are two boys.
An older barefoot boy plus a younger shirtless boy equals two boys.