He is speaking specifically of answering those in the world, but should we not be even more gracious to those in our family?
The Greek word Paul uses, translated "grace," is charis, which means "graciousness, of manner or act, especially the divine influence upon the heart, and its reflection in the life." Matthew Henry's commentary says, "Grace is the salt which seasons our discourse, makes it savory and keeps it from corrupting."
The words that come from our mouths reflect upon us more than any other facet of our lives. When we gossip, are those words seasoned? Are they "savory" to the ears of others? When we speak in a hurtful manner to our family, both physical and spiritual, are those words "seasoned"?
Think of it this way: If we are living sacrifices, and if the altar is God's table, what kind of dinner-table conversation would be appropriate while sharing a meal with God? Revelation 3:20 tells us that we will have the chance to dine with Christ. If we live our lives as living sacrifices, then we are always before the altar of God. Our actions, especially our speech, should always be done as if we are carrying on conversations at the table with Christ.