35 is considered "advanced maternal age", where there is more risk to both the mother and baby. Given that it takes ~2 years to make a baby, ideally you should start having kids no later than 35 - 2n, where n is the number of kids you plan to have.

Does this go for both the mother and father?

Obviously not. For women, the clock is ticking ever so fast once they hit 30.

For men, it's really not, until they are 40+, and if in good health, even 50.

The best time is the time that's right for you.

I wish we'd stop perpetuating this myth of "the time that's right for you".

Biology unfortunately or fortunately requires women to have healthy kids until a certain age, and the more women are aware of it the better for them (that is if they plan on having any)

The twenties [citation needed].