Father and Son are NOT naked in the opening scene
I've seen a few posts here describing the actors portraying Alexei and his father as "naked" or "nude" in the film's opening scene. This is incorrect - as the scene progresses and Alexei is being cradled in his father's arms, it's clear Alexei is wearing briefs, while his father appears to be wearing pajama bottoms (notice the folds of material on his knee).
As for the relationship between the two men and whether or not it's homoerotic, we should consider the definition of the term. In this case "homo" means "same" (as in same sex), while "erotic" is defined as "of or causing sexual love, especially tending to arouse sexual desire or excitement." It should be clear to anyone who's seen FATHER AND SON that Alexei and his father have a very intense relationship. They're close in every possible way - physically, emotionally and spiritually. But are they sexually close? Or, to put it another way, are they *beep* each other? Personally, I don't think so. The two obviously share a special bond (not to mention DNA), but they're becoming aware of the fact they may not always be together. A military posting may take Alexei away, employment opportunities may force his father to relocate, or perhaps marriage (or even death) will separate them. I think director Alexander Sokurov is looking at the relationship between two individuals who've been close all their lives & care deeply for one another, but who suddenly realize that (one way or another) it can't last forever.
However, let's use the term another way - is it possible some people might find watching FATHER AND SON a homoerotic experience? Well, let's face it - the film gives us two very attractive muscle hunks who are frequently in each other's arms, and just as frequently gazing soulfully into each other's eyes. And yeah, I know a few people who've gotten VERY turned on by watching this movie. But that doesn't mean Alexei and his father are having a sexual relationship - it just means that some people get off on films that feature man-to-man tenderness & intimacy. However, it's worth reiterating that I don't think these two are doing "the wild thing." They're good-looking men, and they're very close, and they're FATHER AND SON.
That's all.
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By the way, this is a very interesting, dreamlike, and (I might add) beautifully shot motion picture. But don't look for a plot here; FATHER AND SON is really a mood piece. It may not be everyone's cup of tea, but I love it.