I think this is may be the same family in the 1851 census
Which would mean that Maria and Frederick both 10 yo in the 1851 census are grandchildren
1851 Census
Registration: District Harborne
Event Place: Harborne, Worcestershire, England
Piece/Folio 2050/323
page: 49
Registration Number: H0107
Joseph Nicholls 68 birthplace Wolds End, Stropshire (birth year estimated) 1783 Head Green Grocer
Ann Nicholls 66 birthplace Birmingham, Warwick (birth year estimated) 1785 Wife
Frederick Nicholls 21 birthplace Birmingham Warwick (birth year estimated) 1830 Grand son (his name and age match the Frederick in the 1841 Census above)
Sarah Nicholls my Joseph Nicholls and Ann's daughter's son Joseph Nicholls born about 1834 and her daughter Margaret Bruyn born 1837 were both christened in Birmingham Warwickshire and in the 1851 Census, it says that they were both born Bm Warwickshire. Sarah's other children born in England were born in Smethwick, Staffordshire and registered in Kings Norton district (the 1841 census for the Kings Norton District has Joseph Nickolls, Ann Nickolls and children in it).