My (distant) Seabrook cousin Jean Cassell in the UK is not a member of this forum but saw your message and asked me to send the reply below.
Malcolm Ward firstname.lastname@example.org ______
I came across John born Guildford 1804 while researching my Seabrooks.No connection found to date. But I can give you some info:
John 1804 St Mary Guildford son of Thomas Seebrook Ann 1806 St Mary Guildford daughter of Thomas Saybrook Thomas Seabrook died St Mary Guildford 1815 aged 46.Must be the same Thomas - no other candidates.
John Seabrook of the Parish of St Giles without Cripplegate b = 16 Nov 1828 Mary Tickner at Stoke-next-Guildfordwits Ann Seabrook, George Tickner.
above marriage traced from 1881 census where he is shown as born in Guildford.
As John did not marry Martha Young until 1833, Mary Tickner must be mother of John 1832
Could find no burial for a possible mother of John & Ann in Guildford local indexes, nor in Stoke-next-Guildford. Let me know if you have any luck here - it might help to trace his origins.