In an answer to a different question on this site, one of our community members once said:
At one time or another, I suppose most of us have suffered from
premature connectivitis syndrome (PCS)--we don't really know enough
yet by which we can well identify a person, yet we want to connect
them to a much earlier place in time.
The wise advice given started with:
Work from a time line on which you specify locations (and/or events).
Pick the point on the timeline where you feel you have solid
information; begin there. When you move from that point in time, think
INCHWORM (rather than leapfrog).
Especially with modern-day genealogy, where we access so many records online, websites try to make it easier for us by indexing names and encouraging us to search for records by name. Very often in the process, context is lost and sometimes it is difficult to determine what records we are looking at.
The problem is compounded when sites like Scotland's People (or findmypast with the 1921 Census of England and Wales) attempt to make family history more affordable for us by charging on a pay-as-you-go basis. Theoretically we pay only for the records we need -- but PAYGO makes comprehensive studies of either places (One-Place Studies) or surnames (One-Name Studies) expensive for the casual researcher.
To sort out a possible same-name problem, it helps to build a table, chart or spreadsheet that summarizes the information of all the sources you have looked at so far. Try to collect as many identifiers as you can for all the individuals mentioned on each document. Original signatures on documents are prized (when we can get them) because sometimes comparing the signatures on documents can disambiguate which document belongs to which individual.
The Genealogical Proof Standard consists of five elements:
- Reasonably exhaustive research.
- Complete and accurate source citations.
- Thorough analysis and correlation.
- Resolution of conflicting evidence.
- Soundly written conclusion based on the strongest evidence
It might be easier to resolve the conflicting evidence if you had more evidence to look at -- in other words, if you learned more about the individuals involved in the records you've collected. Take the records you already have and "wring them out" to get all the possible clues -- the addresses at which people lived, the occupations of the individuals, etc. and make a list of all the identifiers that might help you distinguish your subject from someone else with the same name. (You've already made a great start by saying "the cerfiticate states the following information" instead of automatically attributing the information to your research subjects.)
Think about what other record sets might shed light on your question. Have you looked for wills and testaments, house history information, accounts in newspapers, or other record sets beside birth, marriage and death records?
For research in Scotland, I highly recommend the free (donations welcomed) conferences hosted by Emma and Graham Maxwell of Scottish Indexes. The conferences are a wonderful way to learn more about researching in Scottish Records. Some presenations and handouts from past conferences are available on the Past Conferences page. Watching case studies can be especially helpful for getting ideas about new record sets to search.