The I Ching hexagram that indicates marriage is Gui Mei, Hexagram 54, “the marrying maiden”, Thunder over Lake.
Gui means to belong to, to return, and Mei indicates a maiden, a young girl, or a younger sister. In northern Chinese vernacular, “xiao mei” refers to a waitress and “mei zi” refers to a young girl. A girl who marries is said to “return” to the family to which she “will belong to” or “destined to belong to.”
A less direct indication of a marriage or a marital relationship could also be Hexagram Tong Ren, Hexagram 13, fellowship with others, literally “together with people”.