I would like to prevent being dependant on one CTO, because fast and efficient progress is too important. Is it possible to hire two CTOs at the beginning? Or will it be similar to hiring two senior developers, who will then fight the whole day about decisions and be less efficient than one CTO? Thank you for your input.
CTO is acronym for "Chief Technical Officer". While it is possible to have more than one Chief, it is unusual (and usually comes with "Joint" or "Co-"). However it happens. Research In Motion (the makers of Blackberry), for example, has 2 co-CEO's.
As to whether they'll fight all day... CTO aren't developers, they're leaders and managers (in their technical fields). You can have one work on one line of products, the other on another, so that they won't interfere with each other.
If all they are going to do is write code - then they're not CTO's, really, so why call them that?
Rather than calling them CTO's, why don't you name them as VP's of Technology (or something similar)? Or name one as a VP and the other as a CTO.
It really depends on your specific scenario though, if they're going to be in charge of two different products or areas, than they're better off being VP's, if they're going to be in charge of technology as a whole, they would be Co-CTO's...although one (or both) of them might take it as an insult to have a co-CTO with them.