There is an 1841 Census entry for West Gallatown in Dysart, which is about a mile inland, at Back Lane. This gaves David Walker 31, Catherine 30, John 11, David 7, Margaret 5, James 2, Alexander 1. David's occupation is given as Linen Handloom Weaver - this was the main occupation in Gallatown.
I also know from the FFHS Death Records CD that a son of David Walker in Gallatown, Thomas Walker, died 27th December 1836. He may belong between John 11 and David 7.
1841 ages, especially children's, are not very accurate. If born 1828 your John should have been 12 or 13, but that's not unexpected for 1841. Also no relationships are given or birthplaces.
There were a number of Walkers in Wester Gallatown, including Alexander 33, Alan 30, and Andrew 41 all married and all Hand loom weavers. It is just possible these are brothers, though only one, Alexander appears in your ancestor's siblings. There is also a John Walker aged 69 Hand loom weaver living with Elizabeth 25. He could be the father of David, especially as if following the usual naming tradition here, John is named after his grandfather.
Again following the naming tradition, Thomas (the child who died early, possibly) could be Catherine's father, as David who follows has his father's name. The eldest daughter Margaret may indicate the name of David's mother.
There is another death entry for St Clair town, just south of West Gallatown in 14th November 1848 of a Catherine, daughter of David Walker, weaver.
Hope this helps.