...smiles at you not just whenever you walk in the room, but anytime you speak or look in his direction.
...will sit in the weirdest position on the edge and corner of the sofa so that one of your cats can stretch out and look adorable (with his claws resting against some very personal spots if he decides to flex them another millimetre) whilst the fragile, probably slightly demented, elderly one clamps herself to his chest and shoulder for warmth and security for anything up to 18 hours of the day, the other 6 being spent either having her squeeze onto his office chair with him or frequently going to sleep on his chest with the stretchy one barging his way up to the top of the bed to nick a pillow and rest his pointy bits against his bald scalp.
...learns how to give you your injections because your hands are too weak and swollen to do them yourself.
...assumes that he's coming with you to any hospital appointments unless you specifically say he doesn't need to - but will book time off work without question if you say you want him to come.
...only mentions when you ask him that yes, when you were extremely ill a few weeks after you started dating because you caught flu whilst on immune supressing medication, he did take a fortnight off work, he did take you to the toilet throughout that time and, yes, you did have your period but, as he'd already provided intimate personal care for his grandfathers when they were dying of cancer (and he was 17 and 19 when that happened), it wasn't a big deal because 'you were really ill and needed help'.