Durham Records Online:
Baptisms, Sunderland District - Record Number: 592063.0
Location: Monkwearmouth
Church: St. Peter
Denomination: Anglican
12 Jun 1807 William Spain, born 23-Mar 1807, 2nd son of William Spain (Shore mariner) by his wife Ann Humphrey (daughter of Ralph Humphrey, mariner of Shore ).

1841 census for Whitburn Street, Monkwearmouth Shore:

Name	Age	Occupation	Whether born in county
William Spain	34	Block Maker	Y
Elizabeth Spain	35		Y
William Spain	10		Y
Jacob Spain	6		Y
Joseph Spain	3		Y
Elizabeth Spain	1		Y

1851 census for 18 Barclay Street, Monkwearmouth Shore:

Name	Relation	Age	Occupation	Where born
William Spain	Head	44	Blockmaker	Durham Monkwearmouth
Elizabeth Spain	Wife	45		Durham Monkwearmouth
Jacob Spain	Son	16	Sail Maker	Durham Monkwearmouth
Joseph Spain	Son	12	Blockmaker	Durham Monkwearmouth
E. Ann	10	Daughter	Scholar	Durham Monkwearmouth
Mary Jane	Daughter	5	Scholar	Durham Monkwearmouth
William Spain	Son	19	Blockmaker	Durham Monkwearmouth
Thomas	Son	3	Scholar	Durham Monkwearmouth
Isaac	Son	2		Durham Monkwearmouth
Dorothy Wrightson	Servant	18		Durham Monkwearmouth

Dorothy Wrightson is William's cousin once removed, a daughter of his cousin Dorothy Spain.

1861 census for 18 Barclay Street, Monkwearmouth Shore:

Name	Relation	Age	Occupation	Where born
William Spain	Head	54	Blockmaker	Durham Sunderland
Elizabeth Spain	Wife	56		Durham Sunderland
Mary J	Daughter	15	Scholar	Durham Sunderland
Thomas	Son	13	Scholar	Durham Sunderland
John	Son	12	Scholar	Durham Sunderland

Is John the same person as Isaac in the 1851 census?

1871 census for 18 Barclay Street, Monkwearmouth Shore:

Name	Relation	Age	Occupation	Where born
William Spain	Head	64	Block and mast maker	Durham Monkwearmouth
Elizabeth Spain	Wife	65		Durham Monkwearmouth
Mary J	Daughter	25		Durham Monkwearmouth
Isaac	Son	21	Block and mast maker	Durham Monkwearmouth