1856 is before the start of statutory birth registration in Ireland (1848-1864) and so you’ll need to rely on church records to trace his baptism. To do that you really need to know a bit more about where he came from, as well as his religious denomination. This site suggests the name is rare and mostly confined to Tyrone & Belfast.
Griffiths Valuation has no Jarvis households recorded in Ireland (1848 – 1864) but there are some Jervis. The name Alexander Jervis appears in Kildare and Roscommon. They be your ancestor but it might be a relative or two.