+ Bellatrix was demisexual, meaning she did not experience sexual attraction without first forming a strong emotional connection with the person. The only person she ever would have lusted over was Voldemort. I'm not sure she was conscious of a physical desire for him (at least not sexually), but she was so devoted that if he'd indicated any desire for it, she'd have jumped his bones in half a second. I can't decide if she and Rodolphus would have consummated their marriage once for tradition's sake, or if they wouldn't have felt it necessary. I'm guessing, given pureblood conservatism, that they probably did have sex on their wedding night to make it "official" but then never again.
+ Bellatrix was profoundly relieved when Narcissa had Draco because it meant that her family would stop expecting her to carry on the Black family line. Not that she would ever have bowed to their pressure (unless Voldemort wanted to be the baby daddy), but it was a relief to have the matter settled once and for all.
+ Narcissa missed Andromeda. She never spoke of her sister, not even to Lucius, but she missed her. When Tonks was born, she sent flowers and a silver, snake-shaped rattle with no note.
+ After the war, Narcissa reached out to Andromeda. Devastated by the loss of her husband and daughter to Narcissa's cohorts, Andromeda refused to have anything to do with her. Nevertheless, Narcissa sent anonymous presents to Teddy on every birthday. On her deathbed, dying of old age, Andromeda finally consented to see her sister. Narcissa came without delay. Andromeda never said "I forgive you," but she said, "Teddy always liked your presents. Same as his mother. Could never get that rattle away from her," and she died with her hand in Narcissa's.