Jealous of sisters wedding date

So my baby sister (who got married at 17 to someone she'd been with for only 3 months the day they got married.) picked the exact weekend my fiancé and I were gonna get married next year. She got married 09-12-15. We were looking at 9-10-16. 
I have always wanted a fall-ish outdoor wedding and September has the perfect weather for it where we live most of the time. 
My older sister got married in August- which we weren't gonna do anyway cuz my guys first marriage, August wedding and he didn't want that again. 
My older brother got married in October- I'd want late October if we did go with that. 
And now my little sister picked the weekend she knew I had picked and always wanted. 
My issue is I never wanted to have a wedding anniversary too close to my siblings because they/or their spouses would try to make a competition out of it- who done it better, pretty much. 
I know it's kinda petty, I don't need anyone saying that. I don't need the negatives. 
I just need some advice on how to go about having the wedding I want without feeling like I have to compete with my siblings/in laws.