My nephew is getting married in July and the wedding is being held at a Greek Orthodox cathedral. Since his whole side of the family is Roman Catholic, is it appropriate for us to receive Communion at the wedding?
From what I understand, unlike the Catholic Church which offers a nuptial Mass, Eastern Orthodox do not combine divine liturgies with their wedding liturgies. (Here is an overview of Orthodox wedding liturgies.) If so, that means that Communion will not be offered at the wedding.
Regarding Catholic attendance at Orthodox divine liturgies, Catholics ordinarily should not receive Communion at Orthodox liturgies. Under ordinary circumstances, the Catholic Church doesn’t allow it; and, as far as I know, the Eastern Orthodox don’t allow it at all.