If your dad has a foster sister is she your aunt and her children your cousins?

Not by blood but if they are close maybe in name. If anything she would be your foster aunt and foster cousins. To some people that may mean something and to others it doesnt. If you want my opinion, if someone treats you good and holds you dear to them(blood or not), appriciate them and be thankful they are in your life. Dont worry about labels or trying to define everyone's place or relationship to you. Remember there's two types a family: The ones who are passed on to you by blood and the ones who have no obligation or responsibility to you but choose it anyways simply kuz u matter and they love u.