The Proto-Indo-European word *bʰréhater-
Word *bʰréhater-
Transliteration brater
Meaning brother
See also Phrygian: ΒΡΑΤΕΡΕ ‘brother’
Phrygian: ΒΡΑΤΕΡΑΙΣ ‘brother’
Lydian: brafr- ‘a member of the commune’
Armenian: elbayr ‘brother’
Old Norse: bryþr ‘brother’
Tocharian B: procer ‘brother’
Proto-Indo-European: *bʰrehatríyom ‘brotherhood’

Other words that might be of interest
*ĝ(e)lōu̯- ‘sister in law’, *gʷénha ‘woman, wife’, *i̯énǝter- ‘husband’s brother’s wife’, *méhₐtēr ‘mother’, *aner-, ner- ‘man, vital energy’, *awo- ‘grandfather, adult male relative other than one's father’, *deh₂iwer- ‘husband's brother’, *dhuĝ(hₐ)tḗr ‘daughter’, *ĝh₂lōu- ‘brother's wife’, *h₂en- ‘ancestor’, *népot- (nom. népōt-s gen. nept-ós) ‘grandson/nephew’, *ph̥atḗr ‘father’, *snúso- ‘daughter-in-law’, *swésōr ‘sister’, *yenh₂ter- ‘brother-in-law's wife’, *wihₓrós ‘husband, man, freeman’, *at- ‘father’, *dheh₁- ‘uncle’, *h₂euh₂os ‘uncle, grandfather’, *h₂/₃orbʰos ‘orphan, heir’, *h₂/₃wed(h₂)- ‘lead in marriage, marry’, *h₄em- ‘mother’, *h₄en- ‘mother, (old) woman’, *hₐekkehₐ- ‘mother’, *hₐnḗr ‘man, person’, *t-at- ‘father’, *wersēn ‘male’, *manu- ‘man, ancestor of humankind’, *m-h₄em- ‘mother’, *népōts ‘grandson, nephew’, *n-h₄en- ‘(old) woman, mother’, *papa ‘father, papa’, *pótis ‘husband’, *r̥sḗn ‘male’, *sm̥-loghos ‘spouse’, *sneubʰ- ‘marry’, *swék̂uros ‘father-in-law’, *dhĝhm̥ón- ‘man’, *ĝénh₁es- ‘family’, *ĝenh₁tōr ‘father, procreator’, *ĝenh₁trihₐ- ‘mother, procreatrix’, *mr̥tós ‘dead, mortal’, *mórtos ‘person, mortal, man’, *neptihₐ- ‘granddaughter, (?) niece’, *neptiyos ‘descendant’, *putlós ‘son’, *potnihₐ- ‘mistress, lady, wife’, *prihₓehₐ ‘wife’, *suhₓsos ‘grandfather’, *suhₓyús ‘son’, *suhₓnús ‘son’, *swek̂rúhas ‘mother-in-law’, *teknom ‘child, offspring’, *widhewehₐ ‘widow’