It appears that Millison is Abraham's daughter and Abram died between 1855 and 1857 when Betty re-married, but that is not the case. The only matching death for Abraham is in 1845, aged 35. Betty must have then found another partner and had two more children before marrying George Sanderson in 1857.
Abraham was actually born in 1811, the son of William and Betty, so about 37 when died.
Occupation Details
From 1833 Abraham's occupation was Collier in Blackburn.4
Knowles was born in September 1844 in Over Darwen.6
Birth Notes
Aged 7 in 1851
Lancashire Birth indexes for the years: 1844 MATHER Knowles KNOWLES Darwen D/8/59
MATHER, KNOWLES KNOWLES GRO Reference: 1844 S Quarter in BLACKBURN Volume 21 Page 47
He died at the age of 58 on March 9th, 1903 in Blackburn.7
Death Notes
Name: Knowles Mather Age: 59 Estimated Birth Year: abt 1844 Registration Quarter: Jan-Feb-Mar Death Registration Place: Blackburn, Lancashire, United Kingdom Death Date: Mar 1903 Inferred Death Place: Lancashire, United Kingdom Volume: 8e Page: 303