Rodolphus Lestrange didn't know where he went wrong. Bellatrix Black by all accounts should have made an excellent wife. She was a pureblood, sorted into the right house, had the right politics, had the right friends...but that was the problem, wasn't it? She was a true believer, a zealot, when it came to the Dark Lord.
She never would have married him if it hadn't been asked of her. She would much rather devote herself to him. Not that their sham of a marriage did much to stop her. Rodolphus was well aware of the rumors. He would have expected more discretion from their glorious leader. Rodolphus wasn't sure how much of what he heard was true, he wasn't sure he even cared.
In the beginning it had hurt him. Of course it had. Not so much the disloyalty but the shame that came with it. What kind of man couldn't control his wife? But Bellatrix wasn't the type of woman to be controlled. She'd made that very clear.
When the rumors of infidelity first began Rodolphus had tried confronting his wayward wife. In retaliation she had an affair with Rabastan and arranged so Rodolphus would walk in on them. No amount of magic could ever reverse the trauma of seeing his brother naked.
That was the end of any hope for a true marriage. Rodolphus hadn't dared to lay a hand on Bellatrix since then. They slept in separate rooms, ate at different times, and kept different company. The only time they acknowledged each other was when their duties to the Dark Lord required it.
In that regard they were excellent together. A perfect team, with no moral qualms and an unshakable devotion to their master. They had so much in common then, but that was also another problem. They were cruel, unspeakably so, and when there were no muggleborns to torture they had to turn to each other for an outlet.
Abuse came from both sides, sometimes with words, other times with wands. If they'd had even one friend who'd truly cared about their well being then perhaps a divorce would have been suggested. But there was no such friend and so they were encouraged to maintain their 'relationship', for the sake of appearances.
Their marriage was the union of two twisted souls who did not belong together, anymore then they could belong to to world. Perhaps it was a mistake, perhaps is was fate, but in the end only death was able to part Rodolphus Lestrange and Bellatrix Black.