A stepfamily is the family one acquires when a parent marries someone new. For example, if one's mother dies and one's father marries a new woman, that woman is one's stepmother, and any children she already has are one's stepsiblings (if they were fathered by your father, however, they are your half-siblings instead of stepsiblings).

In many fairy tales, stepmothers are portrayed as wicked, evil, and hating their stepchildren. This is perhaps best seen (or at least most well known) in Cinderella and Hansel and Gretel. Also, negative connotations used as in "stepmother's blessing"—the painful bits of skin that sometimes come away from the edge of a fingernail.