If twins were born would they both have down syndrome? if so expain

we estimate that identical twins with Down syndrome occur at the rate of 1 or 2 in a million pregnancies and non-identical twins at the rate of 14/15 in a million. If the likelihood of having a twin or twins with Down syndrome is also linked to a family history of twins, to age or to assisted pregnancies, we presume these factors will play a part in increasing the risk for some individuals.

1. is through mitosis2.dna replication