The age of the Milky Way Galaxy is about 13 billion years, but our Solar System is less than 5 billion years old. If the Sun had been one of the very first stars, how would the Sun and its aging differ?

Answer: the Time frame of light traveling k from earth to sun is lower than that milky way galaxy.

Explanation: our solar system is a member of the milky way galaxy, the ages of these planets are measured with the way light travels. It takes more time for light to travel around the milky way and to the milky way galaxy than the the sun.

Because Sun has lower metallicity

Explanation:

Metallicity means the presence of elements in any objects heavier than hydrogen or helium in abundance.

Though the Milky way galaxy is of about 13 billions years, Sun is only 5 billion years old because it took time to collect dust and gas for the formation of such big celestial body. Its metallicity is low which means it has only lower mass elements which took time to combine in order to form heavier elements thus producing light and heat.