If they want to… ^^
Buddhism emphasises respect of all religions and that the foundation of all religions is basically the same.
My best friend is a Buddhist but he occasionally feels an urge to attend Catholic mass. On the Buddhist side of that, there’s no one who can say he shouldn’t.
If you are already Catholic, or Christian, Buddhist teaching can still be studied without having to “be” Buddhist yourself. There’s no reason you’d have to stop going to Church.
for more on the topic, you can click: