I suspect Martina and Edward were brothers.
There's quite an age difference between Edward and Martin.
From censuses, year and places of birth are:
Martha b 1777 - 1781 (age 60 rounded in 1841)b Oxon
Martin b 1784 Ascott.
George b 1789 Oxon poss Little Milton.
Edward b 1807 (Little) Milton
Priscilla b 1807 Ascott (Edward's wife)
If Edward and Priscilla Cruch were cousins, then somewhere there is Edward's father who would be Martha's brother.
Possibly related are:
Mary Crutch b 1786 Askot (sic) Oxon - unmarried, living, Chearsley, Bucks on 1851 census. In 1861, Mary is with her daughter and son in law (James and Mary Piddington) in Upper Winchendon. Her status is widow, but it does look as if something has been overwritten. birth place is Asket, but definitely says Oxon not Bucks. Maybe enumerator or son in law more familiar with spelling of Askett near Monks Risborough
William Crutch b abt 1814 Ascott, Oxon - chimney sweep, living Watlington with wife Sarah and family in 1851.
Another Cruch family living in Stadhampton in 1851
John b abt 1816 Brookhampton
wife Ann b abt 1823 Stadhampton, children Henry, John and Sarah. Also in household Thomas Impey visitor 4 years old b Stadhampton.
In 1871 this John is a widower living with his unmarried brother Thomas. Thomas was born in Ascot, Oxon about 1813.
So quite potential family building up.
Added
Thomas born Ascott looks like the one with Martin in 1851 (unmarried son), so Thomas and John would seem to be Martin's sons.