In this case, including is the right translation. The two members of the royal family are included into the four ministers being replaced.

Of which would be the appropriate translation in this case:

Original text: Le mois passé, le roi du Bahreïn a procédé au remplacement de quatre ministres dont deux membres de la famille royale.

My translation: This past month, the king of Bahrain has proceeded with the replacement of four ministers, two of which are members of the royal family

Further reading: https://www.cnrtl.fr/definition/dont