Around 15/20 people from my year at sixth form went to my uni the same year I did, it was insane the amount of people I know before I'd started. Some of these people were really good mates, I've known them and been in the same class at high school since I was 13 ...
It's not been a bad thing at all, I wasn't living in halls with most of them, and It was great because in my first year, I met people from my flat/halls, and then my course and societies, and then had my close friends from home and all the people I met through them ...
Also - I've lived in a house of 5 in our second year, where 4 of us have as I've said known each other since we were teens ... This wasn't because we didnt go out and meet other people, it's because we're genuinely good mates, and know each other really well and knew we would be able to live with each other. It worked out much better than a lot of other uni houses where people meet people and agree to move in and then find out the hard way during their second year that they dont get on ...
Just don't cling to them, go out and meet all the people around you, and see what happens!