Hi Isabelle,

About the family’s religion the marriage of Samuel and Margaret appears to be where the two religions came together see my post on 24/10/2016 at 6:12 pm:-

We have a C of E baptism for James born 1850. There's an RC one too. This says that Samuel was a Protestant, therefore Margaret was already RC:-

Event Type: Christening
Event Date: 20 Oct 1850
Event Place: Douglas, Isle of Man
Father's Name: Samuel Stewart (Protest)
Mother's Name: Margaret Wright
God Parents: William Maxwell & Mary Wright

Link: familysearch.org/ark:/61903/1:1:XZ1K-SXG

About the Irish roots yes County Down is now in Northern Ireland then it was in Ireland. In both situations the county was and still is in the UK. Travel within the UK does not create immigration passenger lists so there are no records of their coming to the Isle of Man. Also see my post on 24/10/2016 at 11:44 pm about the Irish roots:-

I can’t find a Samuel son of Samuel baptised c1830 in County Down. Perhaps the reason Samuel and Margaret left Ireland was because they wanted to marry but would have experienced some hostility where they lived because they were different denominations. I can’t find a baptism for Margaret either. Church of Ireland, Roman Catholic and Presbyterian records decrease in availability the further back you go.

Col