hello,
I got the same problem. And I've tried a lot of things.
Restart some quests before, restart the further quest 3 or 4 times. I have tried to start Kindred Judgment quest with console command, tried to start and end the quest before Kindred Judgment with console command .. Nothing works

Kindred Judgment will not start. Serena will not talk to me about Lord Harkon. Lord Harkon and Isran will not die.
I have found many many entries about this bug. But no solution.