In Fantastic Beasts: The Crimes of Grindelwald, one of the most compelling plot lines that have been outlined in the trailers, is the backstory of Nagini. We learn that Nagini was a female witch, more specifically Maledictus.
Now, on Reddit, a user has explained a possiblity that ties Nagini into Voldermort's family.
They began: “People have speculated that Fantastic Beasts will tie in to Voldemort’s birth, due to the fact first movie takes place in 1926.
“Voldemort (Tom Riddle) is born of Merope Gaunt on December 31st 1926.
“A poster seen in the first Fantastic Beasts movie speaks of a circus called the Circus Arcanus moving from New York to Europe on December 13th 1926.”
They then shared a quote from Harry Potter and the Half-Blood Prince, where Mrs Cole is talking about the birth of Tom Riddle: “I remember she said to me ‘I hope he looks like his papa’ and I won’t lie she was right to hope it, because she was no beauty – and then she told me had was to be named Tom, for his father, and Marvolo, for her father – yes I know, funny name, isn’t it? We wondered whether she came from a circus.”
Circus, hey? We know from the trailer that Nagini performs in a circus.
It's clear that she is beautiful, so why would anyone refer to her as not beautiful? Well they have an explanation for that too.
“Perhaps Merope was ugly due to her upcoming permanent transformation into a snake.
“Perhaps Merope gave her child to an orphanage before faking her own death and running away so she would not harm her child after her snake transformation. The Gaunts, after all, are descended from Salazar Slytherin – what better family to carry a snake curse?”
If Tom Riddle is the child of Maledictus, it would explain Nagini's almost maternal relationship with Voldemort in all the books.
They explain: “If the two were able to communicate via parseltongue, this theory would explain why Voldemort is so fond of Nagini, entrusting her to become a Horcrux.
“Maybe the reason Voldemort was able to regain a baby-form was that his own mother, Nagini, gave birth to him again. As Nagini contained a piece of Voldemort’s soul, maybe Voldemort’s soul joined with Nagini’s piece of soul, which would later be given a body through childbirth.”
All we know is that Voldemort's backstory into his family parentage is one of the most compelling parts of the HP books, so if that is further explored, we would be VERY happy.