Sigvart Gabrielsen born Stavanger 1854 (??)

A new member, I am looking for help please tracing my Norwegian ancestors. Sigvart Gabrielsen married my grandmother Agnes Arnesen in Cardiff in 1926, and they subsequently lived in Newport, S Wales where both died. His marriage certificate states age as 56, hence born 1870. I traced Sigvart's name in Norwegian State Archives. The Stavanger Parish Register gives a record with date of birth 30 May 1874, baptised 21 June 1874. The "Sjomansruller" for Stavanger also gives Sigvart with this date of birth and enlisted on 11 March 1892 (roll no 6845) with voyages in 1892 (Globus), 1893 (Jerusalem) and 1894 (Agathe) including calls in port of Cardiff, which fits well. (Sjomasruller also gives an Alexander Gabrielsen roll no 5583 who could be his brother). "FamilySearch" yields five siblings including Alexander and father Gabriel Gundersen born 1818 (or named as Gabriel Hadland in at least one record), and mother Anne Olene Tollaksdr. born 1830. I cannot locate them or any of Sigvart's siblings in any census or other records. I would appreciate help tracing Gabriel and Anne, and his siblings; any living descendants; and history of the vessels he sailed in. Thanks in anticipation David Yaw London, UK