Reverend Robert McGonagall Sr. was a Muggle and Presbyterian minister who lived in Caithness, in Scotland, during the early twentieth century. He married Isobel Ross, and together they had several children: Minerva, Malcolm, and Robert Jr.; all of them wizards.
At some point during his teens, Robert became captivated by the high-spirited Isobel Ross, who lived in the same village. Like his neighbours, Robert believed that Isobel attended a select ladies' boarding school in England. In fact, when Isobel vanished from her home in the school months, she was attending Hogwarts School of Witchcraft and Wizardry as she was, unbeknownst to Robert, a witch.
Marriage and family
Deeply in love, Robert and Isobel (then aged eighteen) decided to elope, angering both sets of parents. They married and had a blissful honeymoon, on which Isobel could not bear to tell her Robert she was a witch, and so the fact remained a secret.
The couple's first child, a daughter, arrived on 4 October, 1935. Isobel, missing her family and the magical world she left behind in the name of love, named the baby Minerva in honour of her own grandmother, a powerful witch. The residents of Caithness found this name extremely unusual and Reverend McGonagall found it very difficult to explain to the members of his congregation why Isobel had chosen it. After Minerva's birth, Isobel became moody, alarming her husband. When Robert consulted his friends, they told him that post-partum depression was not uncommon for new mothers to go through, and that it would soon pass. However, Isobel only grew more withdrawn, sometimes hiding away with Minerva for days on end.
What Isobel was actually trying to do was keep Robert from catching sight of any of the subtle signs of being magic that Minerva had displayed from her very first hours of life. One night, she finally broke down under her husband's gentle questioning, and, in tears, retrieved her wand from where it was hidden and showed him she was a witch. Robert, while shocked by this revelation, did not love Isobel any less after it. Isobel also explained how she was bound to keep the existence of the wizarding world secret from Muggles by International Statute of Wizarding Secrecy.
While the couple still loved each other afterward, they never regained the sense of trust they once shared, something which Minerva, an extremely bright, observant child, soon recognised.
Isobel and her husband eventually had two more children: Malcolm and Robert Jr.. In time, both proved to be magical, and Minerva readily helped her mother teach them that they could not go around showing off their magical powers, and helped her cover up the accidents their magic sometimes caused.
Personality and traits
Robert McGonagall was a serious, upright and honest man, and seemed to be amiable and close to his parishoners. His daugher Minerva was noted to be similar to the Reverend in temperament and personality and, as such, one can presume he was strict, stern and clever.
- Pottermore (Mentioned only)