Wiktionary
one flesh
n. (context idiomatic English) Two people united by marriage.
Usage examples of "one flesh".
Our bodies melded together into one flesh, one body, as if I were sinking into his chest.
Adam and the Garden are one flesh, and the power of God is in them both.
Adultery, in Latin, means to approach another man's bed, by reason of which those that once were one flesh abandon their bodies to other persons.