Nope. And they can't create one (except Venice). In one of my games whole Ireland (and part of Scotland) was one big republic. But there were no "Serene Doge" of Ireland, though they had money and piety for sure.
If you have Doges as vassals in your big empire it becomes somewhat annoyance... they want title but you can't give it to them nor they can create it. Sigh.
Thanks for the help!
Is there any way to mod this problem?
Would be cool to have king-tier republics in my empire now that i'm making 171 ducats per month....