Hi, do you know whether Robina's son was born in Peebles too?
I looked on scotlandspeople and couldn't find a likely birth record in Peebles for her son. It might not have been under the surname Archibald though
However, there is a record for Robina Scott Archibald's in 1923 in Earlston.
There is also a probate for a Robina Scott Archibald, wife of a John Archibald in 1936 in Earlston on ancestry.co.uk who could possibly be a relative. (I don't know how much information you have)