Double Twins

My daughter will be attending the Twins Bat Mitzvahs. Are we expected to pay double?
They are classmates of my daughter, but not really socialize outside of school together. Normally, the gift for Bar or Bat Mitzvah a classmate (ie, no, a good friend) said that the cost for the customer to cover participation party. Since no single party, we have to give a gift twice? Is money more or less.
Yes – the gift giving is a gift to the child. Since two children, there must be two gifts.
Just For Laughs – Double Twins