This is one of the most discreet, but also the strongest, forms of feline attachment: not very demonstrative, but very significant.
He senses your emotions
Cats are surprisingly sensitive to their humans’ emotional state. If you’re stressed, tired, or tense, your cat may instinctively come to sleep near you. Not to “cure” you, but because your presence soothes them as much as it reassures you.
This silent presence then becomes a form of mutual comfort, almost imperceptible, but very real.