MY SISTER, MY BRIDE
‘The Song of Solomon is a beautiful, poetic presentation of married love. Chapter 4 deals with the wedding night; as the bridegroom and his bride consummate the marriage, they speak to each other tender words of praise and affirmation. Four times, in speaking to his wife, the bridegroom calls her “my sister, my bride”—or “spouse” in some translations. “How delightful is your love, my sister, my bride!” (Song of Solomon 4:9; see also 4:10, 12, and 5:1).
Solomon had not married his actual sister, so we can dispense with that theory right away. Rather, the term sister was a common expression of closeness and love. In ancient Egyptian love songs, “my sister” was a customary name for a female lover. It was a term of endearment that emphasized the permanence of the relationship (a sister never stops being a sister). In giving his bride a double title, he shows her double honor: he loves her with the passion of a spouse and with the purity of a sibling.’ (GotQuestions)
Perhaps the only thing as wonderful as this is for a man to hear: My brother, my husband. You have to know about this to know about this.
“How delightful is your love, my sister, my bride!”
“‘This explains why a man leaves his father and mother and is joined to his wife, and the two are united into one.’ Since they are no longer two but one, let no one split apart what God has joined together.” Jesus