there is a tendency, discussed at spanish prepositions, to treat as indirect objects those direct objects which happen to refer to people. hence some speakers say "le/les vi" "i saw him/her/them" when referring to people and "lo/la/los/las vi" "i saw it/them" when referring to things. this is known as "leísmo de persona" and is permitted by the real academia española (rae) only when used in the masculine singular (i.e. "le" to mean "him").