Is called a squib.
They are referred to as 'squibs.' Mr. Filch is a squib, as is Mrs. Figg.
Witch or Wizard.
There are many terms used in the Harry Potter series to describe magical and non-magical people. Magical people are referred to as witches and wizards. Non-magical people are referred to as muggles. A pure blood has no trace of muggles in his ancestry. All of his family, including both parents are wizards. (Ron, Sirius, Draco, Neville) A half blood has one muggle-born parent and one wizard parent. (Harry, Voldemort) A mudblood is a derogatory term used to describe someone who is born with muggle parents, but are born with the ability to perform magic. (Hermione, Lily Potter) A squib is someone who has wizard parents but does not have the ability to perform magic. (Argus Filch, Dumbledore's sister Arianna.)
You can call your child whatever you want I mean it's yours.
A firstborn child is the first one born to a couple or individual; normally the eldest child.
There is no title for them and they are basically adressed as students, although you can call them a witch or wizard even though that applies to the entire magical being community.
A Squib is a person who is born to at least one parent who possesses magical abilities but do not have magical abilities of their own.There are two mainly known examples of Squibs in the Harry Potter series, these are Argus Filch (the caretaker who works at Hogwarts) and Arabella Figg (a member of the Order of the Phoenix) who lives in Privet Drive near Harry and was asked by Dumbledore to keep an eye on Harry while he was young and was not at Hogwarts.It is said that although Squibs do not possess any magical abilities such as the ability to use a wand, they are accepted usually into the magical world. Squibs are unable to see Dementors. Mrs Figg, when asked about the presence of Dementors in Little Whinging, lied in order to get Harry off the charges. Squibs normally marry into muggle families and all Muggle-Borns are descended from Squibs
Muggle..or if you're refering to a half wizard like Hermonie, a "mud-blood" as Malfoy likes to call her.
grand wizard.
It is up to you -- you may even make up a word like 'Squib-born'.
A man who possesses magical powers is often referred to as a "sorcerer," "wizard," or "mage." These terms can vary depending on the cultural context and specific traits of the character. In some traditions, he might also be called a "warlock" or "enchanter." Each title carries its own connotations and associations within the realm of fantasy and folklore.
A squib