Tony was already old. Moreover, Manny had already become the acting family head. He did not want his sons to turn against each other, so in the end, he still did not allow the illegitimate children to return and inherit the position.
He thought that, during his lifetime, if he could find that child, kill him, and obtain the family head’s token, then his grandchild, who was even more ruthless than his son, could inherit the token.
That way, the position of Longbottom family head would continue