George R.r. Martin said this quote

Some woman, no doubt. Most of them are. He favored Jon with a rueful grin. Remember this, boy. All dwarfs are bastards, yet not all bastards need be dwarfs. And with that he turned and sauntered back into the feast, whistling a tune. When he opened the door, the light from within threw his shadow clear across the yard, and for just a moment Tyrion Lannister stood tall as a king.