Alec was deeply in love with Bertrand. Warped and grotesque, yes, but true. They were everything to each other for the first eighteen years of their lives, and it's not an exaggeration to say Bertrand broke Alec's heart by refusing to go with him to Bali. Now, granted, Alec's upbringing alongside Bertrand was tantamount to being groomed into that incestuous relationship, but I'd still count it as romantic love.

If Isabelle hadn't been born, I don't think Alec would have ever loved again after Bertrand. He's borderline aromantic, and I think Bertrand's betrayal and death broke something in him.