(1) If the heirs are appointed mutually or if for one of them the others are appointed as substitute heirs, then in case of doubt it is to be assumed that they are appointed substitute heirs in the proportion of their shares of the inheritance.
(2) If the heirs are appointed mutually as substitute heirs, then in case of doubt heirs who are appointed to a joint share of the inheritance take priority over the others as substitute heirs for this share of the inheritance.