Bellatrix needs her husband. (a statement you’ll never hear come out of her own mouth). The two were married when Bellatrix was barely over eighteen. She has not provided him an heir. Patonically or not, they have spent over a decade operating as a team. Rodolphus recently helped her kill the minister of magic, and she's staying at a safehouse outside his property.
In my conception, I believe the two operate both as each other’s partners and fiercest rivals. At times, they challenge each other, but usually, it's them against the world. Bellatrix wears the Lestrange name by force, but she never allowed herself to be truly dominated by her husband. Even so, I imagine the tides have changed somewhat since Bellatrix’s recent rescue.
Is he protective of her? Does he enjoy rubbing it in? Both? Preferably, he'd be a staunch follower of Lord Voldemort and have similar aspirations as his wife when it comes to bringing the Dark Lord back. OR, alternatively, he would believe that he and his wife could take their fallen Lord's place.
Beyond those ideas, I leave rodolphus's construction to you. Is he more diplomatic than his wife? The ice to her fire? Or are they both unstoppable blazes?
I honestly do have a bunch of ideas as to their dynamic, but I want to leave this as open as possible for anyone interested. The suggested face claim is James McAvoy, but I'm open to anyone who fits the role. Feel free to message me here or on discord (akakios #0975) to discuss more!