hi
i have dual citizenship. 2 of my grandparents were born in ireland. my family was / is lucky we still have cousins in ireland they were able to get my grandmom's birth certificate. you need that, marriage license , your birth certificate, your parent or grandparent birth certificate and bunch of other forms. go to the dept. of state website. good luck its a long but well worth process. it took me about 10 months.