What evidence proves that the sun is a second generation star?

Answer 1

In all probability, the Sun is a third generation star, based on the amount of "metals" within.

Answer 2

The composition of the Sun, with heavy elements like carbon and oxygen, indicates that it formed from the remnants of previous generations of stars that had already undergone fusion. This is in contrast to first generation stars, which would have had only hydrogen and helium. Additionally, studies of other second-generation stars in the Milky Way provide further evidence for the Sun being part of this later stellar generation.