Could another spelling be Sebire?
A number of people by the name Sebire arrived ib Australia from Guernsey in the 19th century:
1850 on Maitland to Melbourne - Henry 21. b.13 Aug 1828 St Sampson, Guernsey, s/o John (Jean) Sebire & Judith Torode.
1853 on Countess of Elgin to Melbourne - brothers Daniel 19, James 19 & Peter 18. Twins b. 28 Apr 1833 St Sampson, Guernsey, s/o Daniel Sebire & Elizabeth Roussel. Their sister Betsey Le Page nee Sebire arrived on the Joshua in 1852 and their brothers Henry 17 and Joshua 16 arrived on the Evening Star in 1854.
1854 on Evening Star to Melbourne - John (Jean) age 23 of St Sampson, Guernsey.
1857 on ? to Melbourne - William Joseph 16 b. 18 Feb 1841 St Sampson, Guernsey s/o John (Jean) Sebire & Judith Torode.
If any of these people are the ones you are looking for then let me know. There is more information on them in the book 'Guernsey Emmigrants to Australia 1828-1899'