Lewis & Short

frāternus, a, um, adj. [frater], brotherly, fraternal.

  1. I. Lit.: sese et amore fraterno et existimatione vulgi commoveri, Caes. B. G. 1, 20, 3: tametsi in ipso fraterno parricidio nullum scelus praetermissum videtur, tamen, etc. … ab hereditate fraterna excludi, Cic. Clu. 11, 31: acerba fata Romanos agunt, Scelusque fraternae necis, of fratricide (committed by Romulus), Hor. Epod. 7, 18; cf.: fraterno primi maduerunt sanguine muri, Luc. 1, 95; so, sanguis, Hor. S. 2, 5, 16: lyra (because given to Apollo by his brother Mercury), id. C. 1, 21, 12: mores, of Zethus, brother of Amphion, id. Ep. 1, 18, 43: undae, of Neptune (as brother of Jupiter), Ov. M. 7, 367: invidia, against his brother (shortly before: fratris invidia), Sall. J. 39 fin.
  2. II. Transf.
    1. A. Of or belonging to a relalive or kinsman: frater erat, fraterna peto, the arms of his cousin Achilles, Ov. M. 13, 31: pectora, Val. Fl. 1, 163: fama, id. ib. 1, 178.
    2. B. (Acc. to frater, II. A.) Brotherly, fraternal, i. e. closely allied, friendly: propter amorem in nos fraternum, Cic. Q. Fr. 1, 1, 3, § 10: pro fraterna illa necessitudine, id. Quint. 4, 16: animi, Hor. Ep. 1, 10, 4: foedus, id. ib. 1, 3, 35.
    3. C. Poet., of animals yoked together: it tristis arator Maerentem abjungens fraterna morte juvencum, of his companion, Verg. G. 3, 518.
      Hence, adv.: frāterne.
      1. 1. In a brotherly manner: quare facis tu quidem fraterne, quod me hortaris, sed, etc., Cic. Q. Fr. 2, 15, 2.
      2. 2. Heartily, affectionately: tibi persuadeas, te a me fraterne amari, Cic. Att. 1, 5 fin.