Correct grammar-both of whom?

The phrase "both of whom" is grammatically correct. It's used to refer to two people or things previously mentioned, emphasizing that both of them share a particular characteristic or are involved in a particular action.

Example:

"The two friends, both of whom were artists, decided to collaborate on a mural."

In this example, "both of whom" refers to the two friends, highlighting that they both share the characteristic of being artists.