Cats are often very particular about where they sleep. They like to choose a spot that offers them some privacy, as well as a clear view of their territory and escape routes in case of an attack by predators. They also tend to select a sleeping partner that makes them feel safe. This could mean that they pick a parent or sibling who provides warmth, or even their favorite human. They may even choose to sleep with a person who shares their own smell, or they might prefer a snorer’s partner if they know the noise will keep them awake. The rhythmic sound of a person’s breathing can be soothing to cats too.
In the wild, cats’ great-great-grandparents would huddle together at night to protect them from outside predators. This huddled behavior has carried over to modern life. Many cats prefer to slumber with their primary carer, or a person who understands their species-appropriate behavior and regularly feeds them, provides water and treats, takes them out on leash and harness walks, and gives them lots of attention.
Some people are simply warmer than others, and so it’s not surprising that cats sometimes opt to share their sleep with a more svelte person. They might also knead the area that they’re sleeping on, which helps to maintain their ideal body temperature as they slumber.