Picture of the Belgian Kings; Collection of the <a href="https://en.wikipedia.org/wiki/Royal_Museum_of_the_Armed_Forces_and_Military_History" class="extiw" title="w:Royal Museum of the Armed Forces and Military History">Royal Museum of the Armed Forces and Military History</a> in Brussels.
From left to right: <a href="https://en.wikipedia.org/wiki/Leopold_I_of_Belgium" class="extiw" title="w:Leopold I of Belgium">Leopold I</a>, <a href="https://en.wikipedia.org/wiki/Leopold_II_of_Belgium" class="extiw" title="w:Leopold II of Belgium">Leopold II</a>, <a href="https://en.wikipedia.org/wiki/Albert_I_of_Belgium" class="extiw" title="w:Albert I of Belgium">Albert I</a>, <a href="https://en.wikipedia.org/wiki/Leopold_III_of_Belgium" class="extiw" title="w:Leopold III of Belgium">Leopold III</a> and <a href="https://en.wikipedia.org/wiki/Baudouin_I_of_Belgium" class="extiw" title="w:Baudouin I of Belgium">Baudouin I</a>.
No machine-readable author provided. <a href="//commons.wikimedia.org/wiki/User:Carolus" title="User:Carolus">Carolus</a> assumed (based on copyright claims).
CC BY 2.5
No machine-readable source provided. Own work assumed (based on copyright claims).