Thomas Gilbert was master of the Charlotte when he arrived at Sydney in January 1788 as part of the First Fleet. He was appointed captain of the Neptune in 1789 to being out another group of convicts. Gilbert and Lieutenant John Macarthur exchanged violent exchanges (including a duel) about who had ultimate authority on board the ship and Gilbert was replaced with Donald Trail at Portsmouth.
Gilbert may have fathered the child born by Jane Langley at the Cape of Good Hope in October 1787. The entry in the log when Langley's daughter was born reads 'Jane Langley delivered of a Girl namely T----G----' giving rise to the possibility that the actual father might be Gilbert. Perhaps he had taken her on board the Charlotte for female company as had Henry Lidgbird Ball with Sarah Partridge. It would account for the absence of Langley's name from Surgeon Bowes list of convicts. Jane may have been sent to the Lady Penrhyn for the delivery.
* information from Mollie Gillen, The Founders of Australia: A Biographical Dictionary of the First Fleet (1989), p 142 and 213
'Gilbert, Thomas (?–?)', People Australia, National Centre of Biography, Australian National University, https://peopleaustralia.anu.edu.au/biography/gilbert-thomas-31170/text38557, accessed 2 December 2023.