son of the same mother:
as Subst., ἀδελφός, ὁ, voc. ἄδελφε; Ep., Ion., and Lyr. ἀδελφεός (gen. -ειοῦ in Hom. is for -εόο), Cret. ἀδελφιός, ἀδευφιός, Leg.Gort. 2.21, Mon.Ant. 18.319:—brother, Hom., etc.; ἀδελφοί brother and sister, E. El. 536; so of the Ptolemies, θεοὶ ἀδελφοί Herod. 1.30, OGI 50.2 (iii B. C.), etc.; ἀπʼ ἀμφοτέρων ἀδελφεός Hdt. 7.97: prov., χαλεποὶ πόλεμοι ἀδελφῶν E. Fr. 975: metaph., ἀ. γέγονα σειρήνων LXX Jb. 30.29.
kinsman, ib. Ge. 13.8, al.; tribesman, Ex. 2.11, al.
colleague, associate, PTeb. 1.12, IG 12 (9).906.19 (Chalcis); member of a college, ib. 14.956.
term of address, used by kings, OGI 138.3 (Philae), J. AJ 13.2.2, etc.; generally, LXX Ju. 7.30; esp. in letters, PPar. 48 (ii B. C.), etc.:—as a term of affection, applicable by wife to husband, LXX To. 10.12, PLond. 1.42.1 (ii B. C.), etc.
brother (as a fellow Christian), Ev.Matt. 12.50, Act.Ap. 9.30, al.; of other religious communities, e.g. Serapeum, PPar. 42.1 (ii B. C.), cf. PTaur. 1.1.20.
metaph., of things, fellow, ἀνὴρ τῷ ἀ. προσκολληθήσεται, of Leviathanʼs scales, LXX Jb. 41.8.
Adj., ἀδελφός, ή, όν, brotherly or sisterly, A. Th. 811, etc.; φύσιν ἀ. ἔχοντες, of Hephaistos and Athena, Pl. Criti. 109c.
generally, of anything double, twin, in pairs, X. Mem. 2.3.19:—also, akin, cognate, μαθήματα Archyt. 1; ἀ. νόμοις Pl. Lg. 683a: mostly c. gen., ἀδελφὰ τῶνδε S. Ant. 192; ἡ δὲ μωρία μάλιστʼ ἀ. τῆς πονηρίας ἔφυ Id. Fr. 925; freq. in Pl., Phd. 108b, Cra. 418e, al., cf. Hyp. Epit. 35: c. dat., ἀδελφὰ τούτοισι S. OC 1262, cf. Pl. Smp. 210b.