FindMyPast has Gavin (42) and Agnes (37) both as born Newmilns.
Alas FMP, like Ancestry, can have transcription errors too.
On this 1871 census FMP has Gavin as Garin - Ancestry has Gavin as Gani.
Quantity over quality comes to mind.
It's always best to look at the original pages if possible.
I often use Ancestry & FMP if I can't easily find a family on Scotlandspeople.
They are useful in that both can be searched using a forename only, age etc.
Once I've found who I think are the correct family I go to SP.
Though sometimes you then have to play about to see what SP has them indexed as!
But it's usually correct - certainly they have far fewer errors.