Since there is more than one house for the Kingdom of Bulgaria, could we add houses? :)
Also, while looking into this I saw some of the kings where styled as princes, not kings
On Ferdinand I Wiki page it's stated he ruled “(…) firstly as ruling prince (knyaz) from 1887 to 1908, and later as king (tsar) from 1908 until his abdication in 1918.”
If that's something we should differantiate between or not? Alexander was only styled as prince and it changed under Ferdinand.
House of Battenberg
Alexander I (1879-1886)
Saxe-Coburg and Gotha-Koháry
Ferdinand I (1887-1918)
Boris III (1918-1943)
Souce: