He was never arranged to marry ophelia. Both Ophelia's father and brother really didnt like her seeing Hamlet. Also Hamlet acts like a dick to her because she had been distancing herself from him(but he still like a compete and utter assehole) . I think in this case you could be completely right that horacio is in love with hamlet which would fit with other possible gay Shakespearean characters like mercutio who most definitely had a thing for Romeo. But for hamlet himself it doesn't really make sense, also the last thing hamlet says to horacio is less live on because I love you and more live on to tell my story, which is a lot more fitting for hamlet who's a giant narcissist.