The two royal houses intermarried for generations, and their ties were very close.
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Literary and historical. Today one says 婚姻 "marriage" or 联姻 "to be linked by marriage".
culture
The word goes back to the Book of Changes: 匪寇，婚媾 "not robbers, but suitors", said of riders who seem to threaten and turn out to have come to propose a marriage.
