There are several witnesses to William & Ann's 1795 marriage:
John Deffell
Henry Davidson
Jannet MacNiel
Sarah Davidson
Justina Davidson
Caroline Davidson.
A couple of things stand out, one is the name Justina.
Is this Justina Anderson now married ?
The other is how the name Jannet is spelt. This is typically a Scottish name & you don't see it spelt this way in England.
Another is the Davidson connection.
Ann Deffell is a minor & her father is named as John Deffell.
You may be able to find a link with these names to the Scottish Family.
Yes Jim and there are more children
the youngest Robert Milligan Anderson d1819 age79
Not a child of William & Ann.