For others who are interested, here is Jim's post from the Eustace Families Association site: "My EUSTICE family arrived in South Australia from Cornwall in 1878. Thomas John and Matilda nee GAY were married in the Helston Registry Office Dec. 28 1867. Matilda was born at Posongath, St. Keverne May 9 1849. Her parents were Abraham and Matilda nee PETERS. Cannot find any record of Thomas's birth but marriage cert. says he was 18 at that time. 1871 St. Keverne (Porthallow Cove) census says he was born at St. Keverne. His parents believed to be John and Christina nee DUNSTON. Children born in Cornwall: Sabina Ann 1868; Clara 1869; Ellen Fadoria 1872; Thomas John 1874; Edith Ann Dunston 1877. Children born in South Autralia ,Emma 1879; Abraham James (my grandfather) 1881; William 1884; and another Thomas John 1887 (the first drowned)."
My reply: Marriage certificate for Thomas John EUSTICE gives his father as John EUSTICE, engine maker in tin mine, who was residing at Wendron Street, Helston.
The 1861 census of Helston shows that on Wendron Street in Helston was a John Eustice 30 who is an engineer in tin mine -- who seems to be the man.But he is listed with a wife Catherine 23 and children, John 5, Ann 3, Catherine 2.No Thomas.This John Eustice was married to Catherine Hodge in 1854 -- after Thomas was born.
I have the complete 1851 Cornwall census index to EUSTICE, EUSTIS, EUSTACE and other variant spellings.There is no Thomas of the right age anywhere in Cornwall.
I also have a complete list of all EUSTICE (and variants) births registered in Cornwall 1837-1880.There is no birth of a Thomas registered 1848-1851.There is an unnamed male registered in St. Austell District in Second Quarter 1848, but St. Keverne is in Helston District.
The only EUSTICE family known to have been in St. Keverne around 1850 was Henry Eustice who married Mary.They did have a son named Thomas, but he was born in 1842.
I also have the index to all Cornwall EUSTICE (and variants) marriages 1837-1851 and there is no marriage between a John Eustice and Christina Dunstan or anything close.
My thought is that John Eustice had a relationship with someone, perhaps a Christina Dunstan, but that they did not marry.In England, if a child is born out of wedlock, the child's birth is registered under the surname of the mother, even if the father is known.So perhaps the reason that you cannot find Thomas' birth record is that he is registered with his mother's surname.
This would also explain why he does not appear in the 1851 census as a EUSTICE -- perhaps he is listed by his mother's surname.Or perhaps his mother married someone else and he was using his stepfather's surname.Perhaps he didn't start using his father's surname until as adult.
I would recommend that you search the christening registers for St. Keverne parish and take note of any Thomas John that was christened, especially any born to an unwed mother. You should search up to 15 years after his birth.
I would also recommend searching the 1851 census for St. Keverne parish page by page and take note of any Thomas who is 0-2 years old -- no matter what the surname.