Do the Romulans and Vulcans actually count as "duel species" (as the poll puts it), though? Because they're more technically the same species and one political faction of them left Vulcan so to go do their own thing, eventually becoming their own entity, but still pretty much the same species save a few minor shifts in the genetic code due to the long isolation between the two.
It'd be like the Canadians all moving to live on the Moon while everybody else stayed on Earth. They'd both be politically and physically divided, but ultimately still humans.
