I've read it many, many times too. I think Shiki's feelings for his brother (Katsura's father) and Katsura were just familial love--but because he was so close with Katsura and also, I think, lonely, that love got a bit too close--I think it was intimate but not sexual. His love for Reiji was the healthy normal kind of falling in love and being sexually attracted to someone (like a boyfriend). Love Mode is one of my all time favourite mangas--the stories are so well done, touching and funny and thoughtful and exciting. All of the relationships are fascinating in different ways. I wish there were a dozen extra stories (like Lover's Mode) for this manga!!
so do i.
i agree with Anne that Shiki's love for Katsura and his father is family kind of love, just like Reiji and his brother. Reiji, when he was a teenager, he loved his brother so much and tried to protect him whatever it takes. that's why he knows Katsura's feeling to Shiki.
I don't know how many times I've read this but I never skip even a single line. I just don't understand who did Shiki love-Katsura's father or Katsura or Reiji? It's so painful to read the part of his death...