You will have to get a copy of - History of the Irish Citizen Army by R.M.Fox, it mentions your relative, Mary Hyland in a chapter on Stephens Green, the book is quite rare but definitely worth reading, it gives a great insight about the 1916 Uprising. If you are based in or near Dublin, there is a shop called Stokes Books, 19 Market Arcade, South Great Georges Street, Dublin 2, you can check if he has a copy, I have had many books from there that have helped me in my research and understanding of the subject
Yes, my great Uncle, Patrick Duffy was in Stephens Green and the College of Surgeons, his future wife, Brigid Davis, was a member of the C.A, and was in Liberty Hall from the beginning and then in City Hall, they both would have known your relatives.
CSM