Namesakes
Frankish and French Kings:
4 kings
King Chlothar I the Old (a.k.a. Lothair) 511-561 
King Chlothar II the Great (a.k.a. Lothair) 584-629
King Chlothar III (a.k.a. Lothair) 656-673
King Lothair 954-986
German Kings and Holy Roman Emperors:
1 emperor, 1 king-emperor
Emperor Lothar I (a.k.a. Lothair) 817-855
King-Emperor Lothar III of Saxony (a.k.a. Lothair) 1125-1137