I agree! "El uno al otro", as they have said, is perfectly correct but bear in mind that it's used when you want to emphasise that the action is mutual. Otherwise, just use the pronoun se and it works perfectly! For example: Se escriben cartas (they write letters to each other) Se quieren (they love each other)

Ellos se aman / Ellos se aman el uno al otro

Se puede decir "el uno al otro" Ex: Ellos se quieren de verdad el uno al otro

Thanks guys! ????