You Bring Happiness! Happy Birthday Card for Sister-in-Law: The message takes center stage on this lovely birthday card for a special sister-in-law. If you have a sister-in-law you love dearly, who brings joy and happiness to others, then this is the birthday card for you to choose. Pink tones and images of butterflies, flowers, and sparkling bubbles give this pretty birthday card a very feminine air. Your dear sister-in-law will be touched by this heartfelt message on her birthday.