Answer: sib

AnswerCrossword Clue
SIBTwin or quadruplet, for short
SIBSister or brother.
SIBAkin.
SIBCain or Abel, for short
SIBKindred
SIBKin
SIBBlood relation
SIBAkin
SIBKin, for short
SIBBro, to sis
SIBAndrew, to Charles
SIBClose kinsman
SIBBlood brother, e.g.
SIBBro. or sis.
SIBOne of the family
SIBRival, perhaps
SIBOne in the family
SIBClose relative
SIBBrief connection?
SIBHousehold member, for short
SIBPerson in a tree, briefly
SIBRoom sharer, often
SIBBro, say
SIBMany a recipient of hand-me-downs, informally
SIBClose relation, informally
SIBFam. member
SIBTwin or triplet
SIBPossible recipient of hand-me-downs
SIBFamily relative
SIBBlood relation, briefly
SIBClose kin, slangily
SIBOne of the kin (Abbr.)
SIBHousehold rival, often
SIBOne you might squabble with in the back seat
sibkinsman; relative
sibrelated by blood akin
sibrelated by blood; akin
sibone's kin or kindred
SIBBro
sibone who has the same parents as another, also SIBLING, SIBB