如兄如弟 Origin — Chinese Character Wiki

rúxiōngrúdì

as close as brothers

如 rú preposition

to be like

to be like; to be similar to; as if
兄 xiōng noun

elder brother

(bound form) elder brother; one's older male sibling
如 rú preposition

to be like

to be like; to be similar to; as if
弟 dì noun

younger brother

(bound form) younger brother; a junior male relative of the same generation; a junior male friend