The Ruler rules with recommendations from the council,
which is headed by a single noble, who is recognized by them
as worthy of the position. He has to have their respect and
the people�s respect. They then speak on behalf of the council
and make recommendations to the ruler, they can bring votes to the
council which they brings it before the ruler. They vote by black/white
pebbles. Otherwise it takes a group of nobles to bring a vote or motion
to the council. The number of nobles is not important just that they are
powerful enough not to be ignored.

The ruler is traditional male (for the late 300 years anyway before
that not as important) but the throne goes to the oldest child.
People have been brought into the royal family before, usually
through marriage (in which they take the royal name) or adoption.
The present king for instance is a member of the family through marriage.
He rules due by the past king, the present queens and nobles allowance.
He became heir to the throne in a time of war, where his skill as general
was needed. These allow show how exceptions come from exceptional
circumstances. It appears to have worked fairly well.