There are similarities between Vulcan and Romulan DNA, of that there is no doubt. However, as Chekov says in The Enterprise Incident" -
"Romulans and Vulcans read almost exactly alike.
There is just a slight difference which --"
The genetic difference between a man and an orangutan may be considered "slight" but that doesn't mean that they can interbreed. We have evidence for various combinations of humans, klingons, romuulans, vulcans, etc. However, we have no example of Vulcan/Romulan. That's not saying that they do not or did not exist. However, in light of NuSpocks statements and OldSpock not correcting him, I would say that it is unlekly. After all, OldSpock spend decades working towards Unification. You'd think he'd say something like "The future of our race may now rest with the Romulans. I must work even harder to being our races together." However, he heads off with 10,000 survivors to start up a new colony. I would say that the evidence shows that the 10,000 includes those Vulcans who were off planet at the time.
