I think your pictures are just adorable Kirsten. Lily must need this comfort and how generous of Luna to still mother Lily willingly I think it must make Luna happy also as she looks so relaxed and content.

Years ago I had an adult male who would happily nurse a younger kitty that we had. It went on for many, many years. The older cat, Harvey grew large nipples and they would stay rather red. My vet assured me it was no problem as long as the Harvey did not object.