That sort of thinking gets a lot of people hurt.
Horses do not "love" as we do, they do not think in the same abstract or romantic ways we do, it just is not part of how they are built.
But they love in their own ways, to a horse to love someone is to depend on someone. Maybe that person brings them food? Maybe leads them to greener pastures, maybe makes the pain go away, or the best of all maybe they make them feel safe. A horse that feels comfortable with someone, in his own sense "loves" that person (or horse). They do get depressed, upset and lonely when they're "loved one" dies or moves away, but like a above poster said they eventually get over it and go back to their old selves. Just be there for your guy, make him feel comfortable and make sure he is eating and drinking okay.
I'm sorry for the loss of your mare
I would also like to think that my horses like me a tad more than the next person.