Wow, such a contrast…that sure challenges astrology. It prompted me to do a bit of twins and astrology googling. I’m sure you’ve already covered this ground and seen the possible explanations for why twins, with very similar charts, can have such different outcomes. From what I can tell theories range from the metaphysical (two different souls) to the psychological (the need to individuate and differentiate from the other twin, perhaps unconsciously playing an opposite role or expressing the shadow potential of planets).
Though it's hard to imagine this could account for their dissimilar personalities and outcomes, I noticed one very slight difference in their charts: David’s Sun is technically in his 4th House, seconds away from the 5th House cusp. Doug’s Sun is just in his 5th House, by seconds.
Thanks for sharing, Francine. Definitely an intriguing mystery for astrology to ponder.