Thanks for your quick responses.
I was aware of the Hort/Hart situation, and searched the Hort's for a possible match without success, and always felt that Hart was correct, as John had Hart written in the Bible.
I knew about the two children that died to John/Susanna, and the mother of Elizabeth was definitely John's sister Mary, and as Mary had died before John/Susanna came to Australia, events here indicated that he was her guardian, as she needed his permission to marry a convict Thomas Smart. He refused at first, but after talks with the church, he gave his permission. It only lasted a short time as he died strangely and is not recorded in the NSW death records. She later married a local farmer Peter Naylor. Local records showed she was Elizabeth Meaton Gibbs, but her death record showed her father's name was Maton or Matton.
I have all the details regarding John's sister Mary's marriage to Joseph Read with their daughter Sarah, and Joseph's marriage to Elizabeth Mitchell. Sarah was Baptised in St John the Baptist Church, Bishopstone on 3 April 1831, and died and was buried on 17 July 1847 at St John the Baptist, Bishopstone.
Didn't know the connection about Penelope Hart, I think with dates shown, she may have been Jane's sister as you suggest.
My main concern is the accuracy of the details I provided for the three Gibbs generations prior to James & Jane Gibbs, namely; Daniel Gibbs/Ann Barnett - John Gibbs/Mary Tucker & John Gibbs/Sarah Nightingale. I believe I am about 90% correct, but it is very difficult going through the Parish Registers for those early times, and marrying them together, without having some doubts.
Hoping you may find something that will confirm a positive outcome.
Thanks again, Peter
