('formal') The person to 'whom' we spoke to was very helpful. = ('formal') The person 'whom' we spoke to was very helpful. = (more commonly) The person 'who/that' we spoke to was very helpful.
('formal') Her brother, 'whom' I met last year, is an attorney. = (more commonly) Her brother, 'who' I met last year, is an attorney.
('formal') To 'whom' did you speak? = ('formal') 'Whom' did you speak to? = (more commonly) 'Who' did you speak to?
(..) Our choices are never easy. Hmm ? # Protect them by thy guardian hand... # ..from every peril on the land. # O spirit, whom the father sent... # ..to spread across the firmament. # O wind of heaven, by thy might... # ..save all who dare the eagle's flight. #And keep them by thy watchful... (..)1997 Titanic