Hi there,
I have the latest version of mc (1.11.2) and forge (forge-1.11-13.19.1.2199) installed. If I try to connect to a realm server, Minecraft shows me the following error: "Your client is outdated and not compatible with Realms. Please update to the most recent version of Minecraft.".
I think this error appears because forge uses the 1.11.jar instead of the 1.11.2.
best regards