Voldermort didn't really "die" when Harry defeated him in the final battle. His will to live was too strong, it seems
He no longer has a complete soul left to attach onto anything... there were only fragments of his broken soul left and they were fading away into ashes
The last remaining fragment of his soul latches on an unknown but extremely strong magical energy source that was detected in the vicinity. With enough time and control, perhaps he may be able to reform once more using this source. Is this deja vu? What is this magical power source and why is it so strong?
A month after the great defeat of Voldermort, Draco finds out that he's carrying a child as a result of his veela bonding. Veelas are able to produce kids regardless of gender, but it's always the firstborn that inherits the magical energy of both its parents, often creating very strong children. With Harry Potter as one of its parents, the magical energy of their first child would be immeasurable.
Jacob Potter is born, a seemingly unknown cursed scar on his cheek with no solid explanation, but it is quickly swept aside as the world finds out that he is no normal child. His magical abilities surpass any known wizard to exist, beating Harry's and even Dumbledore's. He is able to cast everything wandless at the age of ten. He is well known in the Wizarding World as the firstborn son of the savior and the greatest wizard to exist.
Jacob is raised as a kind and proper child. But the older he gets, the more he feels unlike himself.
At age 12, Jacob realises the imaginary voice inside his head telling him what to do and how to feel isn't so imaginary anymore.
He pieces things together and he wished he never tried to go after the truth
Voldermort is a part of him. Or is he Voldermort? He isn't sure anymore. He isn't sure of anything anymore. But he knows the immense rage and hatred in him is detrimental to his family, the only thing Jacob cared about
Jacob hears of a myth in school — the one who finds the cursed vaults would find the thing they desired the most
He needs to cut off this... Connection he shares with the Dark Lord. Before he hurts his parents. Before he hurts Ollie and Lyra. Before he hurts the only thing that's important to him — his family
Jacob Potter mysteriously disappears without a trace, no note, nothing left to his family and goes to find the cursed vaults.