Julie, the first thing you should do is order the LDS film for Inishkeen RC parish, 0926053. Peter and Eileen's marriage would probably not be there, as marriages are included only for 1839-1850 and they probably married 1865-1870. However, baptisms are listed for 1837-1880, so the children should all be there. (Baptismal dates may occur before birth dates if there was a delay in registering births, as there often was, and ages in the 1901 census are pretty unreliable.) You could also look for the civil record of Peter and Eileen's marriage, as civil registration of Catholic marriages began in 1864. First you would have to find them in the index, which your local Family History Center may have. (Inishkeen is in Dundalk registration district.) The entry in the index will lead you to the registration itself. Diane