Hello,
In 1911 Sydney Sedunary was in the Temperance Hotel in Oxford St, Southampton and was a ships steward. From my research his real namewas
Samuel Francis Sedunary.
Encyclopedia Titanica has a full history.
http://www.encyclopedia-titanica.org/titanic-victim/sidney-francis-sedunary.htmlHis father was Thomas Theodore Sedunary (1861-1900) and mother Sarah Radbourn/e who Thomas married in 1882
The 1891 and 1901 show Samuel/Sidney at home in Newbury with 3 siblings.
Widowed Samuel Sedunary b 1833 is with them in 1891. Thomas looks to be Samuel's son from the 1881 and 1871, so yes, you seem to be right. That is the link.
The 1841/1851 have Joseph and Ann with both Samuel and Jane as children. 1861/71/81 has Samuel married to Elizabeth of Caversham
Familysearch has Samuel bap 1830 as son of Joseph and Sarah, and Jane bap 1843 as dau of Joseph and Ann.
Berks fhs Marriage Index has Joseph marrying Sarah Chitty in 1827 and to Ann Mattingly in 1837. (Also has Thomas Theodore marriage to Sarah Radbourne)
Berks fhs Burial Index has Sarah's probable burial in Hurst in 1836 aged 42, Samuel, in Speen in 1892, and one for Ann Sedunary age 38 of Friar Street Reading in 1853. In 1851 Joseph and Ann were living in Friar Street and Ann was aged 37, so this looks to be her.
A Joseph Edward Sedunary married Mary Ann Hall in Camberwell Reg Dist in 1853, so this must be his third wife. You will need the marriage cert to be sure of the right Joseph.
I hope this helps clarify. I am not a relation. Just interested in the families of those on the Titanic. I have handled Sidney's watch when I worked for the Maritime Museum, Southampton. I can send you all the censuses by private mail if you don't have them.
Yours
Vicwinann