From Longman Dictionary of Contemporary Englishblood relationˈblood reˌlation (also blood relative) noun [countable] FAMILYsomeone related to you by birth rather than by marriage
Examples from the Corpus
blood relation• He could be the next-door neighbour, a friend, a blood relation.• The midwife toad has a blood relation, the northern midwife, much alike in appearance. 