SPOILERS from Harry Potter and the Cursed Child ahead! This article is meant for fans who've either seen the play or read the script book. If that's not you, read on at your own risk! Major plot details from Cursed Child ahead...
So, there's something we need to talk about. Harry Potter and the Cursed Child revealed quite a few things about the characters we've come to know and love (or love to hate) from the first seven books. And one of those reveals involves the romantic (or at the very least, physical) relationship between two of the most notorious villains in the story.
I am, of course, referring to Tom "Lord Voldemort" Riddle and Bellatrix "married to Rodolphus" Lestrange.
Apparently, they were a thing. Enough of a thing to produce a child.
Naturally, we have questions. So let's get those out of the way...
1) Wait, seriously?
2) Did Rodolphus know this was going on?
3) Was he ok with it?
4) Did Voldemort know about the child?
5) Was this a romantic relationship? Or just a physical one?
6) Was this a one-time thing or was it going on for a while?
7) Were they trying to make a baby? Or was baby Delphi a surprise?
8) Ok, is this really that surprising?
So many questions, not enough time in this play to answer all of them. Fitting to the theme of the eighth story in the Harry Potter universe, in which the offspring of the original series' lead characters take center stage, Voldemort and Bellatrix's daughter, Delphi, plays a major role in Harry Potter and the Cursed Child, and yet, the story doesn't really have time to fill us in on all of the details centering on her existence.
But let's lay out what we do know about the situation.
Delphi was born in Malfoy Manor before the Battle of Hogwarts. So we know that she was born before Voldemort died. Taking into account the timeline of things, the Battle of Hogwarts was in May. Unless I'm forgetting something, the last time we actually see Bellatrix before that is when Harry, Ron and Hermione come face-to-face with her at Malfoy Manor (when they find Ollivander, Griphook and Luna). According to the Lexicon calendar, that would've been around mid-March. So either she was pretty far along then, and Harry just didn't notice. Or she'd already had the baby by that point. Either way, Voldemort was on the search for Hallows at that time. So it's possible he never had the chance to meet the little Voldebaby.
As for whether or not Rodolphus knew about the situation, we can only speculate as to whether he was aware of it while it was happening, actually consented to the affair, or was completely in the dark. We do know that Rodolphus Lestrange was the one to track Delphi down after he got out of Azkaban, and tell her who she was. So at some point, he knew that Delphi was Voldemort's daughter, and I have to imagine he was ok with the situation if he made it a point to find her. Also, from the way Delphi describes Rodolphus as Bellatrix's "faithful husband," I'm inclined to think there wasn't much bad blood between the two Lestrange over the infidelity. Maybe he even signed off on it. Being the surrogate father of the child of Voldemort might have come with perks.
And that brings us to the matter of the nature of Bellatrix and Voldemort's relationship. It's not something I want to picture, especially on Voldemort's end. Let's not forget, he was hairless, with red eyes and slits for nostrils. He had the whole snake look down. Who knows what else was going on there. But can anyone say they're really surprised that Bellatrix and Voldemort were a thing? She made her affection for the Dark Lord very clear at every turn, both by the way she spoke to him, and about him, so it's not that much of a shock that Bellatrix would've been into Voldy. What's more surprising is that Voldemort had an interest in her, or anyone for that matter. His main objective seemed to be on immortality. Romance and other pleasures of life never seemed all that important to him. Then again, maybe producing a child was one more step in his efforts to secure immortality, and Bellatrix would've been the ideal candidate to mother his child, being one of his most loyal supporters, and a pureblood from an old wizarding family. But given Voldemort's disdain for most of his family line, it's hard to imagine him being super keen on extending it. So it's also just as possible that Delphi's conception was unintentional.
Because of the structure of Harry Potter and the Cursed Child, and its emphasis on timelines, there isn't a lot of time to go into detail about the daughter of Bellatrix and Voldemort. But I imagine J.K. Rowling will have more to say on her (and what will become of her) someday. It's impossible to believe we'll be left not knowing anything more about the Dark Lord's dark daughter.
In the meantime, Cursed Child does fill in a major blank about just how close Voldemort and Bellatrix were.