In 1714 he married Martha Innys, the daughter of a Bristol merchant and they lived in London until his retirement from his grocery business in 1732.
He, like his father, Roger Cossins, was an active member of the Worshipful Company of Bowyers in the City of London.
On retirement he bought the old Elizabethan manor at Redland in Bristol and an estate attached of approximately 42 acres.
They had no children and on Martha's death the house and estate were inherited by her brothers, Jeremy and John Innys.
Much of Cossins' estate was sold off by subsequent owners of Redland Court and housing development occurred on the land in the 19th century.