I don't go for random homosexuality theories in FF games! (The theories about Kuja were enough)

BUT I can see some points. I don't think Sephiroth and Cloud had any kind of love for each other! But as for Zack. They were certainly close - close enough for Zack to dress Cloud (who was, at the time, incapacitated) and follow up by helping to shape his life. Enough that the guy even decided to immitate him in the end. He was most likely being a really good friend, but other thoughts do occur...