qīn​shang​jiā​qīn

to cement ties by marriage

Senses

亲上加亲/ 親上加親 qīn​shang​jiā​qīn (also qīn​shàng​jiā​qīn) to cement ties by marriage

To strengthen an existing family connection through a new marriage, such as between cousins; also means to become even closer through multiple layers of kinship.

References

variant 亲上加亲/親上加親 亲上成亲/親上成親