Each of her aunts and uncles have a family unit of 1 son + 1 daughter + 1 aunt/uncle = <<1+1+1=3>>3 people.
Iris has a total of 3 uncles + 4 aunts = <<3+4=7>>7 aunts or uncles in these family units.
So among her aunts, uncles, and cousins, there will be 7 family units * 3 people in each family unit = <<7*3=21>>21 people.
Including her mother and brother, there will be a total of 21 people + 1 mother + 1 brother = <<21+1+1=23>>23 people coming to her party.
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