[1]

People Say That Having Sex At The Peak Of Ovulation Causes A Woman To Have Multiple Birth.is It True?

[2]

How Do I Know The Time Of Ovulation Peak ?

There is no time during ovulation that makes it more likely for twins than another. Twins come about in a couple of ways... either a single fertilized egg splits (identical twins) or two eggs are released at ovulation, or one very soon after the first, and both become fertilized (fraternal twins).
To know of the "peak" of ovulation you would require medical assistance, even to know if someone is definitely ovulation requires medical assistance. There are several signs that your body is preparing to ovulate, and most likely has, however... but it is difficult to try to pinpoint exactly when this happens outside of a couple of days.

Twins are more genic or done by science today, there isn't a way to have twins by trying to have them, its more a roll of the dice then anything, even some people who have the gene don't get to have them. So if twins is what you want and u or your partner don't carry the gene, then maybe try arifical insimanation. (I believe that's how its spelt)