Sorry I can't be more help wiht this. This is a HUGE study that will entail a lot of research to predict it statistically high. First one will have to study the ins and outs of the psychology behind homosexuality and as there are different motivations for it, that' will be quite complex. And, psychology may not have enough information about that yet. Then those factors will have to be understood astrologically. That's the easy part for a skilled astrologer. The larger part for a skilled astrologer is learning the psychology of homosexuality.
I think he is not gay because, Sun is in 10th, which is very male. Saturn in 10th, is very neuter. Saturn aspects sun to only 16 out of 60 points, thats insignificant. If saturn was square from the 4th from sun, the aspect would be very strong, but still, sun in 10th, not to likely. So we don't have the important point of Saturn aspecting sun and 10th to any significance.
Can you provide the birth details of this chart?
I must have mixed somethign up when I looked at it. I was tired and pressed for time. According to the basic rules, I would think this person had a good chance of being gay. But you say, not a sign of that. Maybe he is still not aware of it, has not come out in himself, or more likley, as I said, we just do not know enough about this subject to be certain in every case.
I dont see a lot of things that would change my mind on this other than just Ketu is closer to the first than its closer to the 7th, so that is a factor we should test on other charts that look gay, but are not. The reason for this is that ketu in first means a person wants to move towards their non physical gender self, so a man in this case, directs towards a woman. Its much more common for men with rahu closest to first to be gay.
take the attached chart of male gay since young. Ketu is in 10th from sun aspected by Saturn. Saturn a neuter is 7th lord and strongest aspect to saturn is neuter mercury. Not enough for a gay prediction, but add Rahu is closer to first than 7th and it starts to pop into place. Saturn and sun also join in Navamsa.
As I said, this chart has a lot of factors that point towards possible homosexuality. Saturnon angle from sun with saturn aspecting 10th is such a factor. This is because that means the male energy is repressed in the person. What is repressed we seek outside. so that's teh basic foudnation for homosexuality in men - thier male side weaker than the female and so they seek the male, not the female in others. As I mentioned, rahu is closer to the 7th, which means he is seeking the female as the 7th is the opposite gender, so a person wiht rahu closest to 7th than any other angle is seeking the opposite gender, rahu closest to the first than any other angle is seeking the same gender. Is that enough to counter the sun saturn? It must be. But n eed to see more cases to verify. This would mean, yes, his male energy is depressed, but still the need to seek female energy is greater due to rahu closest to 7th. The depressed male energy is indicated by his behavior that you described. Maybe if he had a more developed female side, rahu closest to first, not the 7th, he would be able to be in his female side in a useful way and be homosexual. As it is, his male side is repressed and he is not in touch with his female side either due to rahu closest to 7th.