could this be him??
POSS GRO Birth MASON, ROBERT - Order
GRO Reference: 1875 J Quarter in CHESTER-LE-STREET Volume 10A Page 691

1881UKC William Mason and Family; England Census Durham > Harraton > District 1 > 8; image 8 of 48 @ancestry.com; Source Citation: Class: RG11; Piece: 4982; Folio: 7; Page: 8; GSU roll: 1342198.
William Mason 52
Jane Mason 52
William Mason 12
Robert Mason 5 son (Jane would have been 47 when born???)

1891UKC William Mason and Family; England Census Durham > Harraton > District 1 > 4; image 4 of 36@ancestry.com; Source Citation: Class: RG12; Piece: 4123; Folio 5; Page 4; GSU roll: 6099233.
William Mason 62
Jane Mason 62
Jane Ann Mason 37
William Mason 22 son
Robert Mason 15 grandson who are parents?
Isabella Mason 13 grandson
Ernest Mason 7 grandson b Fatfield