Hi,
I am a little confused. Who is your Peter Young?
As far as I can see for Peter Young who married Agnes Lurton, you have a pretty clear family as given by other contributors.
You say he is 8 in 1841 and 18 in 1851, but in fact if he is born in 1828 he is 22 or 23.
As far as I can see he is probably the Peter who is aged 22 in Duns in 1851.
As other contributors have said you only need to check a couple of records on SP to confirm all this.
The original records have a lot more information on than any transcripts and are essential for any research in Scotland.
Finally dont rely on anyone elses research, everyone makes mistakes, even the people filling in the forms!
Happy hunting