Learn Italian: Lo scrittore era vecchio quando è morto, ma è nato povero. - The writer was old when he died, but he was born poor.

era (imperfect tense) describes an ongoing state or background condition in the past; he was old for a period of time. Dying (è morto) and being born (è nato) are specific, completed events that happened at a precise moment, so they use the passato prossimo.

Why do morto and nato use è as their helping verb instead of ha?

Both morire (to die) and nascere (to be born) describe a major change of state or a life event. Verbs of movement, state, and change of state take essere (to be) as their helping verb in the passato prossimo, rather than avere (to have).

If the writer were female, what would happen to the words morto and nato?

They would change to morta and nata. When a past tense verb uses essere as its helper, the past participle ending must agree with the subject's gender and number. The adjectives would also change, making the sentence: La scrittrice era vecchia quando è morta, ma è nata povera.

In English we say he was born. Why is it translated as è nato instead of era nato?