2nd child concern

Hi mummies. I'm in my mid thirties and a second born. Just would like to rant a little. In a few days, my younger sibling who is in her late twenties, is going away on a vacation with her friends. Why is it that my parents allowed her to go on overseas trip while me, at that age, they have alot to say when i said i want to go on a trip with friends? Why is it that they always have doubt in me? Why is it when it comes to my younger sibling, they somehow are ok with it? Just felt like there's an unfair treatment over here.