1. You won't always share a home with her.
I haven't had this happen entirely yet, but I got a taste of it when I was a freshman living on campus. I stayed on campus most days of the week, and so when the weekends rolled around, I'd go home to see my family and do laundry, but I still felt like I missed out on so much that my mom and sister did during the week, whereas before I never missed anything because we were all under one roof all the time. I've since moved back home to save money, but I realize that while we still share a home now, I will one day live apart from my sister again, and it's going to be weird and sad and I'll want my sister back.
2. You might have to watch her get hurt.
Unfortunately, I have seen my sister get her heart broken by guys she's dated. I've seen her feel so miserable and it breaks my heart. I have seen her so aggravated by stupid stuff that happens at work, and I want to smack whoever thought it was okay to be so rude to my baby sister. I just want what's best for her, and while I want to chew every single person out that has ever made my sister cry, I have to stand back because it won't make things better. I have to let her make her own mistakes (even though I have a tendency to try and play mom and give advice), but I also have to be there for her, which is my job as her big sister.
3. You might not see her as much because she'll have her own friends and life.
When you're in elementary school and sometimes middle school with your sister, you share everything. You go to the same school, she may have some of the same teachers you did, and you see her in the hallways. You might share some of the same friends if you grow up in a neighborhood with a lot of kids your ages. However, once you get to high school and college, and start working and taking different classes, or in the case of college, going to completely different schools, and making different friends and having different schedules, it's harder to see them as often as you may like because of that. I know sometimes I want to watch movies or hang out with my sister, but she's busy at work or with her friends, and sometimes I get too busy with work, school, and my friends. It's a part of life, but after twelve years of having someone around constantly, it's odd to not have that. I'm happy that my sister can be her own person though, and I'm pretty proud of the kind, smart, and beautiful person she is.
4. You might get to be an aunt (or uncle, guys!) one day.
I have been blessed by my sister with the most adorable little niece I could have asked for. She is precious and I love her so much. I am so glad I get to watch her learn new things and get cuter every day. I also get to watch my sister be a mother to that sweet little girl, and it's interesting to see how she wants to parent her daughter. I hope that everyone who has siblings that want children one day can be just as lucky as I am to have beautiful nieces and nephews.
5. You will always have a friend.
Even though I argued with my sister a lot as kids (and still do, now), we got along for the most part. She knows me better than a lot of people do. She can count on me to support her when things get tough, and I can count on her. We grew up together, since we aren't that far apart in age and have the same family. We went through the same struggles with family and some with friends and school. We laugh at a lot of the same jokes, like a lot of the same things, and she and I give each other the best presents, since we know what the other would love. I plan on having her as my maid of honor whenever I get married, because I can't see anyone else being a better friend to me than my little sister. Love you Dodie.