Hello Peter,

To confirm parents usually you need to know children :

1825 John KM
1827 Knealey ( son , later changed to Cornelius ?) KM
1830 Robert K Andreas
1832 Jane Elizabeth KA
1834 Ann KA
1836 Mary KA
1839 Esther KA
1839 Ann KA (????)

Jane's parents John and Esther , so if John Colvin's father also John , could confuse naming. Jane called fourth daughter after mother , not first daughter.

There is only one match born Peel , Kirk German ( His 1851/1871/1881 census states Peel or Kirk German) :

John Colvin married Ann Quayle 28/2/1797 Kirk German , he of the parish , Ann from Kirk Michael. Children :

Mary ch 5/12/1797
John ch 19/5/1799
Matthew/Matthias ch 16/11/1800
Joseph ch 10/04/1803

Mary and John christ. shows John only
Matthew and Joseph shows mother Ann Quayle.

John dies 30/1/1803 (before birth of Joseph) and is buried at Old St German cemetery.

There is a will dated 1803 which confirms the four children and shows the children's Guardians are Uncles Thomas Colvin and William Quayle.

On 1841 Census Cornelius aged 14 is with grand-father John Kneale who is 65-69 in Andreas and uncles John and Philip and aunt Mary.

Esther's maiden name was also Kneale , married 26/11/1798, Kirk Andreas , both of that Parish

Cheers
David