Hello Roger, I am so appreciative that you looked into this. John Craven had at least 2 younger siblings, Daniel and Laurence and I think they all came over at the same time and with their mother Mary. She died in 1852 in Louisiana.
Family info, confirmed by Obituaries and US Census shows birth of John as 1823 in Roscommon, Daniel in 1839. I am just finding out about Laurence.
That does seem to be a large gap in age. I wonder if they were half siblings from different fathers.
Daniel and Laurence remained in Louisiana.
John came to the US in 1846, married Mary Finnegan in Louisiana in 1848, had 2 children there and eventually moved to the Central Valley in California in 1856 and had many more children, including their youngest, my great great grandfather Thomas Craven.
Mary Finnegan, b.1826 was also from Roscommon. Her parents are named as Elizabeth (1791-1867, died in Athleague Parish, Roscommon) and her husband Michael Finnegan b. 1784,died 1860. This is all info from my Louisiana cousin Trees. I have reached out to them to understand how they verified this.