Complex sentence: Currently sixteen of the member states are Commonwealth realms with the Head of the Commonwealth also as their head of state, five others are monarchies with their own separate monarchs (Brunei, Lesotho, Malaysia, Swaziland, Tonga) and the rest are republics.
Split into simpler sentences: Currently sixteen of the member states are Commonwealth realms, with the Head of the Commonwealth as their head of state. Five others are monarchies with their own separate monarchs (Brunei, Lesotho, Malaysia, Swaziland, Tonga) and the rest are republics.