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 फ्रेंड्स at the start of term feast. (Well actually just Peter becomes they're friend but आप get the point.) Remus doesn't befriend them until later that साल but he is already फ्रेंड्स with Lily. When they do become फ्रेंड्स Remus is instantly चार्म्ड द्वारा 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...