She is the second artificial human, between her and her twin brother. Gero’s experiments on her do not impede her ability to reproduce, as evidenced by her giving birth to a healthy daughter, Marron.

Is Android 18 stronger than Goku?

Android 18 is very likely on the same level as Piccolo or maybe slightly stronger or weaker. Android 17 on the other hand is definitely stronger than SSJG Goku but not stronger than SSJB Goku.

Is Vegeta older than Goku?

There is no doubt that Vegeta is older as Goku was only an infant (about 0-1 yr old) when he was sent to Earth, while Vegeta was already fighting in another planet (about 5 yrs old), so Vegeta is about 5 yrs older than Goku.