Santino Allegri is the oldest son of Antonio and Adriana Allegri. Four years after Santino was born, Adriana had identical baby girls named Ada and Anastasia. Two years after the girls were born, the Allegri's had their youngest child, a boy named Alonzo. By all outward appearances, the Allegri's were a normal family. Antonio was a moderately successful businessman and Adriana was a housewife. However the Allegri's had a dirty little secret... they were members of a powerful Mafia clan. Antonio wasn't a businessman and Adriana wasn't a housewife. Antonio was a hitman and Adriana had her hands in corrupting politicians and the police.
Santino didn't like what his family was doing at all but he didn't have much choice. If his family found out he was a good guy, he'd be outcast. And at 12 years old, that's not an option. So Santino acted like he was ready and raring to get into the business. He was a model son. But it was all a ruse. He hated his family, but he didn't see a good way to get out of it.
Santino attended Beauxbatons Academy of Magic, where he was sorted into Ombrelune. It was at Beauxbatons that he met the love of his life, Emilia Di Bernando. She was also Italian, and also tied to the Mafia. But while Santino's family was in Palemero, Emilia's was in Naples. Emilia was a fifth year, while Santino was a sixth year. The pair quickly fell in love and started dating. On the day of Emilia's graduation, Santino proposed. Emilia accepted and the pair were married in December of that year.
Not long after their marriage, Emilia became pregnant with her first child. That's when things came crashing down around Santino. He wasn't about to let his child live with the Mafia. So he betrayed his family. He went to the cops and told them everything and became a mole. It wasn't very long after that the cops stormed Santino's childhood home. As Santino was the only one graduated, he was the only one not home. Santino's entire family was arrested and they all thought Santino was smart enough to escape. Which he was. Santino and Emilia fled Palemero and settled down in Mirto, one of the bigger wizarding communities in Italy.
Eventually Emilia gave birth to her eldest son, Michelangelo Santino. A couple years later, Emilia had twins. A boy named Enzo and a girl named Mesalina. Then a year or so after them, Emilia had their last child named Gabriella.
Things continued as normal for the Italian family. After getting his family arrested, Santino was offered a job as an Auror, which he declined. He wanted to distance himself from the underworld much as possible, so he decided he wanted to help the victims. He became a healer at the magical Italian hospital. Unfortunately for Santino snitching on his family put a target on his back. But his family was left alone. However Santino still worried so at some point he decided enough was enough and talked with Emilia about moving someplace safer. England, specifically. The couple agreed and the Allegri family left Italy for good.