brucelosis on Family Tree Circles

I am researching my wife's family history. We have a family bible which was passed down through her mother's side of the family. This bible lists two generations of McIllwraiths as indicated bellow:

John McIllwraith[b 1836] his wife Mary Ullin[b. 1830] and their children Latitia[b. 1858], Catherine[b. 1859], Robert[b. 1861 - d. 1863], John[b. 1864], Mary[b. 1866] and James[b. 1869].

Though we know that Latitia married a Richard Stewart in 1878[my wife's great grand parents], we can find no further information about the McIllwraith family, where they were from, other ancestors or what happend to the rest of the children.