Thirty-third-generation Bay was crisis generation, the point at which all the changes from old race to new race began to come together and become manifest. It was also an unstable generation, neither new (though "Bay" meant "new") nor completely old. The changes took their toll. Many a line ended at thirty-third Bay. Once past thirty-third, the danger of the line ending was past, and even chance no longer held the reins of their directed evolution, since all Bays greater than thirty-third generation had the power to choose the sex of their offspring-and chose a son. That was one of the changes. But continuing past thirty-third was difficult, so rare as to only have happened once-in the Mercer line. Many lines ended at thirty-third, the Brekks' being only one of those many. Thirty-third-generation Bay Ven Brekk was the last Bay of his line. After sixty-six generations of breeding—thirty-three to Bay and thirty-three more—they'd come to nothing. Kaela Stewert did not want the same happening to his own line. Teal must sire a son, a thirty-fourth-generation Bay. Not that it mattered for evolution's sake, for his people's sake, since the Mercers had produced the Trieath. But for pride. Because he was a Highlander. Highlanders were the leaders and the breeders, the ones who caused the changes, the fathers of the new race. Lowlanders bore daughters and common sons. Lowlanders were the people, the followers. One son, that was the Highland way, the only way for change. If more than a single son was born, the changes did not occur. Although the physical characteristics were unchanged by the birth of brothers and sisters, the line ties were weakened and diffused; the mental and emotional links branched off in divergent ways, many taking energy from a single source. A Royalist was affected by those of his own blood, by someone who came to be in the same womb or from the same father. For a Bay to suddenly gain a brother or sister would be like putting a cold molecule next to a heated one—like a drain of consciousness, a sharing of line memories and strengths, a splitting and splintering of the line. An end.I'm not quite sure how I got hold of this - one of Meluch's other books is on Ian Sales' list of Mistressworks, and I enjoyed a 1998 short story of hers too. I got the book via Bookmooch back in the days when that still worked, so I must have had a specific recommendation.
There's lots of interesting stuff here, but it doesn't quite all hang together. Our hero is the product of an absurdly long-term genetic experiment (his race is long-lived as well, so 33 generations add up to a very long time indeed); he falls out dramatically with his home people and heads off to join the Earth space navy, where he rapidly rises to become a supremely gifted commander. He narrowly escapes certain death several times, has deep relationships with people who don't really seem to matter all that much, and suffers horrible losses of comrades and family which seem to leave him rather cold. A slightly odd book, but I believe the author went on to better things. You can get it here.
This was the sf book that had lingered longest unread on my shelves. Next on that pile is Smallworld, by my old friend Dominic Green.