I'm working on a friends tree (which is proving very interesting!!

)
I have John Houghton Hague as an artist (1841 to 1934) on all census docs and so can definately link him with the family. On "Googling" to see if I can find pictures of his work (I have) I found one reference to him being the brother of Joshua Anderson Hague (1850-1916) (have found lots of his works too!).
The reference to the arstists being brothers is on a website about another artist (Jackson - who may also be related?) BUT I can't tie Joshua to John or John's parents/siblings on any census.
How do I prove or disprove the relationship?
John Houghton Hague was son of Samuel (born c 1805 Oldham) and Esther (born c1805 Newton, Manchester)
Other siblings were Ellen Houghton Hague (born 1844 Manchester), Thomas S Hague (born 1839 Manchester) and Edward (born c 1841 Manchester).
I have Samuel, Esther and the siblings on all the censuses -
1841 Deansgate, Manchester
1851 Deansgate Manchester (Thomas & Edward @ School in Dunham Massey)
1861 Newton Heath, Manchester (no Joshua)
1871 Siblings now moved to Oldham
Any suggestions as I'd love to prove the relationship?