Possibly died. 35 deaths from Mary Brook between 1853 and 1861 in Huddersfield. George, but not Mary was his grandperents in 1861
BROOK, MARY 1 GRO Reference: 1855 J Quarter in HUDDERSFIELD UNION Volume 09A Page 180 or BROOK, MARY 3 GRO Reference: 1857 S Quarter in HUDDERSFIELD Volume 09A Page 151
General Notes
In 1861, after her parents died, brother George was living with his grandparents Job and Lucy. Mary is missing and had probably died.