Harry Potter, Severus Snape and Albus Dumbledore go back to the past to change the timeline.
The method they choose to use means Albus has to blood adopt Severus who has to blood adopt Harry, so they can go back to when Albus was much younger.
The first time around they have traced the Gaunt Family back to the 1870's when Albus is in his 40's.
He was born in 1825, being 166 years old in 1991 when Harry Potter first went to Hogwarts.because of the blood adoption of Snape and Potter, they can exist back then long before they were born.
They Imperio the Gaunts and take control of them. They do the same to the Riddle family and have them start a breeding program to merge their families. Within 100 years when it was about time for Tom Marvolo Riddle to be born, he was not born, but instead twins were born both average power wizards.
One day the twins, Jack & Zack go exploring in their neighborhood and discover that they can speak to snakes.