Yes, that seems to be the way it is, although many will argue that it wasn't a choice, they 'discovered' that about themselves. I am also sure that they have no clue as to the depths of the trap they are putting themselves in.
There is very little data given in this story to do any in-depth dissection of the information. The son he married is now in his late 20's. How the age ranges of the two other identified-as-gay children fit in the story is not stated just as the sex of the two is not mentioned. Nor do we have a definitive statement from the other two, just this "minister's" say-so, which may only be an attempt to justify his act by covering it with some liberal touchy-feely..
If we accept as truth the statement that 75% of his children are gay there are some conclusions that we can correctly draw, and some very plausible speculations that could be offered.
First conclusion is that these odds are off balance. With generally 2-3% of population identifying as homosexual, to have 75% of siblings so identifying is way beyond the distribution curve. With developmental psyc's telling us that a child learns gender-identifying characteristics from that sex parent, a highly statistical conclusion can be drawn that this 'minister' failed miserably in presenting a clear version of 'man-ness' that his children could identify with.
There could be many scenarios that combine to produce this affect. Possibly the father was so involved in his 'ministry' that home things were relegated to the back burner leaving the sons (making an assumption for the sake of the example) to seek out male companionship and acceptance from another and opening them up to possible sexual molestation (a statistically high percentage of homosexual-identifying males acknowledge a sexual encounter with an older male often around onset of puberty.) Possibly the father even if he was 'there' was just distant and cold, again offering a skewed image of man-ness (and conveying a messed up idea of a Father God as well.) Either of these is a viable conclusion if only because of the high percentage of affected children (meaning whatever male image example he portrayed it affected all or most all of his children - as opposed to just one feeling ignored and rejected.)
We can engage in suppositioning a myriad of possibilities but we are not offered sufficient information to go much further. It is unfortunate for these children that very few who follow this path are able to "change their tune" as you say and in a large part because there is no desire to change once they have tied their self-identity to the 'gay' horse...
True enough.