Initial posting pair of results with a Genetic Distance of 12 on 37 markers and a match of 29/37: the odds are extremely low
that they will share a common ancestor at 300 years. No one I know would consider this to be an indication of recent common ancestry and if you were to come up with additional test results and paper trail proof that this pair actually do have shared ancestry in 300 years - you'd be cited as the most extreme case ever found
Second pair of results have a genetic distance of 4 on 25 markers or a 23/25 match: Again, this is not an indication of recent shared ancestry. It is theoretically
possibly (and I do know of one similar case that had a GD=4 on 25 markers) that these men share a recent common ancestor - but it is very doubtful. The first thing I'd do is upgrade both men to 67 markers and see how they compare
Standard matching is GD=4 or less on 37 markers or GD=6 or less on 67 markers. Comparisons at 25 markers are "iffy" and not even worth doing at 12 markers unless you know the paper trails connect.
Why don't you read through the relevant sections of DNA the Smart Way at www.worldfamilies.net/smart