Kindred of the half blood shall inherit the same share which they would have inherited if they had been of the whole blood, unless the inheritance comes to the intestate by descent, devise, or gift from one of his or her ancestors, or kindred of such ancestor's blood, in which case all those who are not of the blood of such ancestors shall be excluded from such inheritance: PROVIDED, HOWEVER, That the words "kindred of such ancestor's blood" and "blood of such ancestors" shall be construed to include any child lawfully adopted by one who is in fact of the blood of such ancestors.
RCW 11.04.035
"Degree of kinship" defined: RCW 11.02.005(3).