His father 's rule was the earliest political union between the two Danubian Principalities ( Wallachia and Moldavia ) , which was to form the Kingdom of Romania in 1881 .
Head entity: kingdom of romania Q203493 25 26 27
Tail entity: political union Q958291 7 8
Relation (head \u2192 tail): P155
Inverse relation (tail \u2192 head): P156