Michael Forbes appears to have died in Dec 1871 and is buried in St Cuthberts, Durham.
I am reposting the 1881 census previously posted by Osprey for James Forbes.
https://www.familysearch.org/ark:/61903/1:1:Q27B-BWBZLook carefully at this as the details for his wife, recorded as Hann, are familiar as those of Michael's wife, Ann. Moreover the two sons showing, John and James would, from their age and place of birth appear to be the sons of Michael and Ann.
So I would suggest that James married his brother's widow, Ann. Now we come to a rather interesting marriage:
18 May 1872 James Forbes married Ann Storey in Spennymoor. Moreover if you look at the co Durham marriage index it shows that these 2 names appeared on the marriage cert - Anne Storey and Anne Parkinson.
James Forbes was buried at Tudhoe, 4 June 1890 while Ann Forbes was buried 17 Dec 1891 at St Cuthbert, Durham but note that her residence on the Bt is given as Wingate.
Now given that Ann died in Dec 1891 you would expect to find her in the 1891 census. Not so but what can be found is a census record for a widowed Ann Storey living in Trimdon. Note her age and place of birth correspond with Ann Forbes in earlier censuses. Furthermore the details for son James correspond with those of James Forbes - age 23, the original showing as born in Framwellgate.
https://www.familysearch.org/ark:/61903/1:1:WJDK-LN2In summary it appears we have 2 further instances of the use of the surname Storey for Forbes. The marriage certs. for Michael Forbes and Ann Parkinson and for James Forbes and Ann Storey/ Parkinson might well be worth obtaining.
William