Have you heard about 'Jong & Out' (Young & Out)? It is thé community for everyone under the age of 18, whatever your sexual orientation or gender identity
In Rotterdam Jong & Out has a meeting every second Sunday of the month from 1:00 pm to 5:00 pm. You are of course most welcome to join! This is how it works: just hop in, have a snack, play a game and meet young people like you. The meetings are not like self help or counseling groups - fun & games and making friends are the main thing. No alcohol is served during the meetings and there are always two supervisors attending. Parents and guardians are also welcome to get to know the supervisors and to ask questions. For more information follow this (Dutch) link. General information in English about the hosting organization you can find here.
If you (also) speak Dutch you can check out this website of the national organization and make your own account.