« Reply #5 on: Monday 29 March 21 15:21 BST (UK) »
Even if he was their biological father, he wasn't married to Fanny, and she was still married to John Chesham so they were legally Chesham. But they may well have been known as Wilson.
birth reg for Louisa
Louisa Chesham jun qtr 1844 Biggleswade vol 6 pg 59 mmn Hare
1851 census as Wilson
https://www.familysearch.org/ark:/61903/1:1:SGCC-J2V
Cornwall: Allen, Bevan, Bosisto, Carnpezzack, Donithorn, Huddy, James, Retallack, Russell, Vincent, Yeoman
Cards: Thomas (Llanbadarn Fawr)
Glam: Bowler, Cram, Galloway, James, Thomas, Watkins
Lincs: Coupland, Cram
Mon: Cram, Gwyn, John, Philpot, Smart, Watkins
Pembs: Edwards (St. Dogmael's)
Yorks: Airey, Bowler, Elliott, Hare, Hewitt, Kellett, Kemp, Stephenson, Tebb