Boyd saw her as his other half. Not his better half but his other half. The person who understood him in a way no one else possibly could. Cora was that for him and she always would be.
Headcanons under the cut.
Boyd's quiet nature is so similar to Cora's, though Cora is more one for confrontation and Boyd would rather let things simmer
Hand-holding and physical touch are extremely important to the two of them, and they both enjoy having some sort of physical connection between the two of them
Cora loves working out and running in the morning, and oftentimes Boyd will join her, but not all the time, he likes a lazy morning every once in a while
Boyd is always intimately in tune with Cora's feelings and emotions
Cora cooks a lot of food, she spent time learning how to make in South America, she really loves it there and definitely takes Boyd there
Boyd also cooks, but a bit less than Cora
Cora is teaching Boyd Spanish and he's getting good at it, but it's taking him time and practice, that Cora is insanely patient with
Nightmares are common in their household and both of them have solid tactics to work through them (Cora likes to be cold after a nightmare and will hold an ice cube in her hand while Boyd likes to be alone but still connected to reality, so he'll sit on the couch while Cora moves around in the kitchen or watches TV)