1. You always had someone to protect/watch over you
Your older siblings were there to defend you from bullies in elementary school, just as they're there now to make sure you're safe. They will unconsciously look after you throughout your life, because that's just what older siblings do. You can trust that they will always have your back.
2. You got to learn from your siblings' mistakes
Before doing something you were unsure about, there was a likely chance that your older siblings had already been there, and done that. Your siblings tested the waters with things before you would have even thought to do them, so you knew what was okay and what wasn't just by observing. You rarely had to be the Guinea pig. Luckily for you, this meant you seldom got in trouble.
3. You got to hangout with the older kids
Your siblings had to bring you along sometimes, which exposed you to what friendships should be like at a little older of an age. Besides feeling cool hanging out with the older kids, you had a good example of what an "older kid" should act like just by tagging along.
4. Your parents occasionally let up on rules
When you're the youngest in the family, parents are less uptight and worried because they had already gone through such experiences with your older siblings. Being the youngest, you tended to have a bit more freedom than what your siblings had. This was super cool for you, but it made your siblings a bit jealous at times.
5. You got hand-me-downs
This probably seems like a bad thing now, but at the time it was "so cool to wear what the older kids had worn." You can't forget that you didn't only get your siblings' old clothing, you got new clothes as well. More for you! You always had a variety of clothes to choose from due to good 'ole hand-me-downs.
6. You learned how to hold your own
While your siblings didn't allow others to pick on you, that doesn't mean that they didn't. Through experiencing this, you learned to hold your own. They did it out of love, of course, and it made you stronger. You learned to fight back and stand up for yourself. You can thank your siblings for that!