Etymology

Rather than as a direct reflex of OE brōþor (nom./acc. pl. usually brōþor), the widespread ME pl. in -e- has sometimes been explained (so TG, GDS, McGee 324, and partly so in (draft) OED3) as showing the influence of the ON cognate; cp. OIcel bróðir, which normally has i-mutation in the nom./acc. pl. brœðr, best accounted for by analogy with the (etymologically regular) mutation in the dat. sg. (cp. also Go brōþar, OFris brōther, brōder, OS brōthar, brōder, OHG bruodar). On the other hand there is some slight evidence for mutation in the nom./acc. pl. in (later) OE (see DOE; the most frequently cited instance is MtGl (Ru) 1.11 <broeþre> (glossing fratres)), which may point to a native analogical extension from the dat. sg. (as Hogg §5.85(4) assumes), as in ON, and thus a possible native origin for the ME form (thus MED, OED2).

PGmc Ancestor

*ƀrōþer- 

Proposed ON Etymon (OIcel representative)

bróðir 'brother'
(ONP bróðir (sb.))

Other Scandinavian Reflexes

Far bróðir, Icel bróðir, Norw broder, Dan broder, Sw broder

OE Cognate

brōþor 'brother'

Phonological and morphological markers

Summary category

CC2bc

Attestation

Pl. forms in <e> are fairly widespread since the earliest ME (from the Interpolations in ASC.E (s.aa. 656, 675) onwards), and found in texts of all dialects; they are especially regular in the N and E (and see OED). VEPN notices only Bretherdale (Wm.) and Bretherton (Lan.) (beside the more commonplace ME pl. in Bretherenhalle, Glo.). There are MnE dial attestations in Sc., Yks, Lan. (see OED and EDD)

Occurrences in the Gersum Corpus

Gaw 39; WA 2512, 5363, 5379

Bibliography

MED brōther (n.) , OED brother (n.) , HTOED , EDD brether (sb.), Dance breþer, de Vries bróðir, Mag. bróðir, Bj-L. bror, Bammesberger 206–8, Orel *ƀrōþēr, Kroonen *brōþer-, AEW brōðor, DOE brōþor, VEPN brōðor