marry below (oneself)
To marry someone who is of a lower social class or standing than oneself. A: "I hear that Mr. Sullivan plans to marry a local fishmonger's daughter." B: "Why would a man of his esteem marry below himself like that?" Janet has a bright future with one of the best law firms in town, so it's beyond me why she's marrying below herself with some fast food worker.
marry below oneself
and marry beneath oneselfFig. to marry someone in a lower social class than oneself. He married beneath himself, but he is happy, and what more is required of a marriage? He did not want to marry beneath himself.