def ineligible_children
      ineligibles = []
      ineligibles |= ancestors | children | siblings | [self] | gclass.all_with(SEX2PARENT[ssex]) if gclass.ineligibility_level >= PEDIGREE
      if gclass.ineligibility_level >= PEDIGREE_AND_DATES and fertility_range
        ineligibles |= (gclass.all - ineligibles).find_all{ |indiv| !can_procreate_during?(indiv.birth_range)}
      end
      ineligibles
    end
def ineligible_children
      ineligibles = []
      ineligibles |= ancestors | children | siblings | [self] | gclass.all_with(SEX2PARENT[ssex]) if gclass.ineligibility_level >= PEDIGREE
      if gclass.ineligibility_level >= PEDIGREE_AND_DATES and fertility_range
        ineligibles |= (gclass.all - ineligibles).find_all{ |indiv| !can_procreate_during?(indiv.birth_range)}
      end
      ineligibles
    end
list of individual who cannot be children according to the ineligibility level in use.
 At `:pedigree` level it returns `self` along with their ancestors, children, full siblings and all individuals that already have father (if male) or mother (if female).
 At `:pedigree_and_dates` level it also includes all individuals who was born outside `self`'s fertility range, if estimable.
 @return [Array]