Filch was Hogwarts' caretaker, but he was also a squib - a Muggle born from wizard parents (which may possibly be the case of Jacob Kowalski from Fantastic Beasts as well).
He was born to wizard parents sometime before 1956 somewhere in the British Isles. Despite his magical parentage, Filch was a Squib, meaning he could not perform magic.
Essentially the reverse of Muggle-borns, Squibs were effectively Muggles forced to live in the wizarding world but unable to fully access it, although they were able to see things hidden from normal Muggles.
It is unclear as to Lord Voldemort's attitude towards Squibs. He had personally noted throughout his life that he aims to purge Muggle-born wizards and witches for "stealing" magic. However, as Argus Filch was allowed to remain in Hogwarts, it is likely they weren't prosecuted as blood traitors.
He married Isobel Ross, a Hogwarts-educated witch and had several children: Minerva, their oldest child and only daughter, and two younger sons, Malcolm and Robert Jnr.
However, like in the real world, some magical members of certain families or groups have biases toward those who do not conform to a "pure-blood" status, such as being Muggle-born, a Squib or, in the case of Rubeus Hagrid, a half-breed. This prejudice may have affected the Hagrid family in a myriad of ways, but Mr.
Hagrid was a pupil at Hogwarts himself and was learning magic along with everyone else - until one horrible day in his third year, when he was expelled (for reasons we discover later on in the series). Although he was able to stay on as gamekeeper, his wand was snapped in half.
McGonagall was born a half-blood witch as her father was a Muggle and her mother a witch. McGonagall began her Hogwarts education at the age of eleven and was sorted into Gryffindor after being the longest ever Hatstall between Gryffindor and Ravenclaw.
Mrs. Norris' looming presence in the Harry Potter series is far too magical for her to be an ordinary cat, and there's enough evidence to support a theory that she's a Maledictus like Nagini. Filch's nosy cat appears all throughout the book series and occasionally in the films.
Neville Longbottom was thought to be a Squib by his relatives because of this, though he proved to be magical. Similarly, Merope Gaunt was called a Squib by her father Marvolo as a slur, due to her poor magical abilities, inhibited by her fear of her father and brother.
Born to a witch mother and a Muggle father, with two older sisters, Gilderoy Lockhart was the only one of his parents' three children to show magical ability. Born to a witch mother and a Muggle father, with two older sisters, Gilderoy Lockhart was the only one of his parents' three children to show magical ability.
Professor Quirrell was a temporary type of Horcrux while Voldemort inhabited his body, which is confirmed in the Wizarding World. It is possible that Voldemort created more temporary Horcruxes, such as the animals he possessed while in ghostly form.
However, Voldemort, after finding out that he taught at Hogwarts, took over his body, subsequently turning him into a temporary Horcrux, though Quirrell put up some feeble resistance. He died in vain while trying to murder Harry Potter in the Underground Chambers.
The once shy and awkward Neville Longbottom showed his true bravery during the battle of Hogwarts and eventually became the head of Gryffindor House while also teaching new students Herbology, his favorite subject.
Who became headmaster of Hogwarts after McGonagall?
Loyalty. Professor Marazion succeeded Minerva McGonagall in the post of Head of Hogwarts School of Witchcraft and Wizardry. This individual became Headmaster or Headmistress some time between 2008 and 2017 after Minerva McGonagall went into retirement as she was "getting on a bit".
Harry describes Umbridge to Sirius Black, saying that she's vile enough to be a Death Eater, despite not being one. Umbridge is also depicted to be a prejudiced person, despising half-breeds and Muggle-born witches and wizards to the point of firing Hagrid due to his half-giant birth status.
The pure-blood wizards and witches featured in the Harry Potter books are almost all supremacists, while there are some of them who do not advocate ancestral superiority; the Potters, Weasleys, and Longbottoms are old pure-blood families, but no known members of these families are sympathetic to supremacist aims.
Harry was the most outspoken, which often landed him in trouble. She steadfastly stuck to the Ministry line that Voldemort had not returned and that Harry Potter's claims were only to get attention for himself.
