"할머님께서 할아버님께 말씀하세요."
Translation:Grandmother speaks to Grandfather.
Not always- that 세 is an honorific suffix. It might be included in a request, in order to 'honor' the person you're asking. In this case, I think it is there because the subject of the sentence (grandmother) is older than the speaker. Also, the 하 is part of the verb stem and the 요 conjugates it at the polite speech level.