What will be, will be - as long as you actually see each other regularly they will find each other.

I have MUCH older brothers and sisters - like about 15 years - we just didn't have squabbles over clothes or who did the dishes last night as we never lived together, but growing up I always thought they were rather cool and it was good having another adult (or bigger person) around that wasn't mum or dad. Probably worse than grandparents in some respects.....

Have fun!