It doesn't seem likely that they are the same people, but it could be possible that William Dowie later became an Easton for some reason. Perhaps he was orphaned and the Easton family adopted him???
These are the IGI entries
WM. DOWIE EASTON Birth: 06 DEC 1834 Christening: 04 JAN 1835 St Nicholas Close St-United Secession Or Scotch Chnewc, Newcastle Upon Tyne, Northumberland
Father: JAMES EASTON Mother: JANE DOWIE
James Easton Spouse: Jane Rierey Marriage: 02 FEB 1834 St John Parish, Newcastle Upon Tyne, Northumberland
1851 census has son William Dowie Easton aged 16 living with James & Jane
1841 has William aged 7 living with them