Hello. You are getting married on my son's birthday! I just had the same experience you did. I got engaged in August, and my younger sister just got engaged a couple days ago. She hasn't made any plans yet, so I don't know if they are going to get married before me or not. I had the same first thought that you did, "I wish they would have waited until I was married so they didn't steal my thunder". Then I thought about it some more and figured her fiance probably had this planned before we got engaged. It takes some time to save up for a ring and pick one out. I am going to pick out all the positives and ignore my first selfish thoughts. They have been together the same amount of time as me and my fiance, it is time for them too. I want her to feel that I am 100% happy for her, because I am and she deserves it. Don't you hate selfish thoughts...no matter how fleeting??
Hi jean! Congrats on your engagement!! Sounds like you situation is very similar to mine! My best advice is to be totally honest with your sister. If she wants to do anything that makes you uncomfortable, just say so. It's not selfish, every girl deserves to have her time in the spotlight and you will both really enjoy it if you do it the right way... Allowing plenty of time between weddings. It may suck for her having to wait a couple a years, but she will realize its better that way in the end.
Best of luck to both of you and let us know how it goes!!