I know a couple where the man is American and the woman is Chinese.
这里的where能否改成in which？
更进一步，当where引导先行词是人的定语从句时，能否都改写为in which 或of which 之类的结构？
couple指一对夫妻时，为集体名词，只是构成这个集体的成员是一男一女而已。和其他成员为人的集体名词一样，当强调整体时，谓语动词用单数，关系代词用which；当强调构成集体的每一个个体时，谓语动词用复数，关系代词用who/whom. 所以a couple后接定语从句，关系代词作主语时，可以用who，也可以用which，取决于大家把couple视为一个整体，而是构成整体的二个个人。一对夫妇中，男的是美国人，女的是中国人。a couple in which the man... and the women... in which是抽象的地址，于是就能用where替换in which, 引导定语从句。以下为几个COCA语料库例句：
However, a couple in which one of the partners has had multiple partners may be at greater risk.
800 subjects responded to a scenario of an argument between a couple in which one strikes the other, bruising their arm.
She says she recently had a case of a couple in which one had a stroke. The other partner discovered too late that she was not able to legally sign for her spouse.
There was a story the other day about a couple where he was deaf and she was blind so they couldn't speak or use sign language but they were happily married for, like, 15 years.
I always distrust a couple where the guy's hair is more carefully coifed than his girlfriend's.
I know of a couple where the woman is battle with cancer, her husband cheats on her because they are not making love anymore.
