Brewer's: Brother German
A real brother. (Latin, germanus, of the same stock; germen, a bud or sprout.)
“Te in germani fratris dilexi loco.” —Terence Andria, I. 5, 58.
A uterine brother is a brother by the mother's side only. (Latin, uterinus, born of the same mother, as “frater uterius,” uterus.)