Happy Birthday Sister in Law Memes: For a woman in her new house, a sister-in-law is perhaps the biggest support and the best friend she has right from the beginning. A sister-in-law helps the newly married bride to get accustomed to the rituals and traditions of the family, the likes and dislikes of everyone, and what to do and what not to. If you have such a sister-in-law in your life, you should be thankful to god and you must not leave any opportunity to make her feel happy and special. Flabbergast your sister in law like no one else by sending funny birthday memes for sister-in-law on her birthday and make her sit on cloud nine like a queen.