The only thing we know about the name Ducroix, is that it has always been said it was Emily's maiden name. (Ammanda and I have both posted about the McCrohons). Briefly the McCrohon family came to Australia with the Kings Own Regiment. John was born 1795 Limerick, enlisted at Cueta as a 15 yr old, 25/5/1810. His service was 3 yrs in Portugal & Africa, 2 years in France, 6 yrs 391 days in West Indies (5/4/1819-1/4/1826), Married at Chatham in June 1826 and then served 1 year and 3 months in Portugal (where son John born) and then 3 years 6 months in NSW. After resigning from the Regiment, John joined the Police Force at Paterson in NSW where he was killed in a horse accident on 6/5/1839.
I have never seen documentary evidence of the birth of John McCrohon who was born in Portugal. I have his death cert which says he was born there. I wonder if there could be anything on the baptism...