Hi
On the 1841 information is pretty basic, there is no relationship given and ages in general ages were rounded down to the nearest 5 for anyone over the age of 15. So anyone listed as 15, could in fact be anything between 15 and 19.
Here is the 1851 census
address Knighton
parish of Canford Magna
John Newman, age 46, farm labourer born Great Canford
Hannah Newman, wife, age 48 born Great Canford
Charles Newman, son, age 9, errand boy born Great Canford
William Newman, son, age 7, scholar born Great Canford
Henry Newman, son, age 6, scholar born Great Canford
James Newman, son, age 4, at home born Great Canford
Cornelius Newman, son, age 2, at home, born Great Canford
Hope this will help.
Nicky