Your g grandfather William Henry Freemantle seems to appear on the 1881 census on familysearch.org. He is the son of William H Freemantle, an unemployed blacksmith living at 3 Albert Road, Peartree, Southampton.
His younger brother Thomas Alfred married my g grandad's sister Jessie Isabel Lillywhite. They had three sons that I know of: Henry 1897, Reginald 1898 and William 1900.
You've probably found this yourself by now, but I thought I'd post just in case you hadn't.