Can step siblings get legally married? Can I marry my sister's sister in law? I am a 16 year old boy and I like my step sister's daughter. Can I marry her? Ask New. 2 Feb When an ex-husband stays in the family, this time as a stepbrother, a writer tries to navigate shifting dynamics. (名) As a noun. A sister who has only one parent in common with you. Hyphenation, step•sis•ter. Part of Speech, (名) noun.