抵足而眠

lit. to live and sleep together (idiom); fig. a close friendship

as close as one's hands and feet (idiom); loving one another as brothers; deep friendship

as close as brothers (idiom); deep friendship

to share the bed; (fig.) to be married

as close as flesh and bones (idiom); deep friendship

(idiom) to sit side-by-side and have a heart-to-heart talk