Remember the last page of the Codex where Altair decides to look into the Apple one last time? He did, and it consumed him. While exploring the Apple himself Ezio finds Altair (his mind, that is, but since they're projections of themselves, it'd seem quite real) half-driven mad with loneliness after all these years. Altair latches onto him, begging him to come back, not to leave him alone in the Apple. Ezio begins to return to talk to him, and then to make love to him.
Ezio/Altair, comfort sex
While exploring the Apple himself Ezio finds Altair (his mind, that is, but since they're projections of themselves, it'd seem quite real) half-driven mad with loneliness after all these years. Altair latches onto him, begging him to come back, not to leave him alone in the Apple. Ezio begins to return to talk to him, and then to make love to him.