Hello. This isn't much but his obituary gives you the married names of two of his sisters and, if the obit is accurate, it appears that most of his siblings predeceased him.
Hartford Courant Feb 6, 1911; page 6 Richard F. Graff, 41 years old, of No. 70 Trumbull street, died at his home Saturday afternoon, after an illness of more than four years. He leaves, besides his wife, three children, Charles, Arthur and Helen Graff; also three sisters, Mrs. C. L. Pratt of Milford and Mrs. W. H. Sears and Miss Minnie F. Graff of Hartford. The funeral will be held at the undertaking rooms of William T. Marchant, No. 53 Ann street, tomorrow afternoon at 2 o'clock. The burial will be in the old North Cemetery.