The Sun and solar system are 4.6 billion years old. The Milky Way Galaxy is about 10 billion years old. Thus the Sun and solar system formed during the last half of the galaxy's history. These regions of space are rich in dust, molecules, and atoms that are packed close enough together to collide frequently. These particles are also close enough together to begin attracting each other gravitationally, which is the key step in star formation.
Large clouds contain enough mass to create hundreds of stars.
During gravitational collapse, the cloud will fragment into separate concentrations of denser areas of gas and dust which will later form stars. Suppose a cluster of stars formed 3 million years ago. If the star cluster is 3 million years old, these stars would have already evolved off the main sequence. Low mass stars take a long time to proceed from the protostar stage to the main sequence stage, so in only 3 million years they would not have reached the main sequence yet. Suppose a new 1-M sun star began forming about 10 pc from the Sun.