This is how I believe a Remus a Sirius got together and it does go up until book 7. Which means there is book moments too.
Year 1
James, Sirius and Peter all become বন্ধু at the start of term feast. (Well actually just Peter becomes they're friend but আপনি get the point.) Remus doesn't befriend them until later that বছর but he is already বন্ধু with Lily. When they do become বন্ধু Remus is instantly চার্মড্‌ দ্বারা Sirius.
Year 2
(Near end of year) James, Sirius and Peter find out about Remus' condition. Which of course we know that they still want to be his friend.
Year 4
Remus stars to develop...