The hardest choice Minerva McGonagall ever makes is to obey the law and not disclose the existence of Witchcraft to her girlhood sweetheart. She is all alone when she makes it, with no other voice to weigh in on the outcome. Everything that comes thereafter pales in comparison. Even sending children to war.
Her two younger brothers find two accomplished witches and start families with them. Minerva works.
When she begins to feel undervalued by the Ministry, she follows Dumbledore to Hogwarts to teach. It is a huge responsibility, influencing young minds, challenging them, preparing them for the world as best she can.
She is not charged with her students’ health education, strictly speaking. Her subject is Transfiguration. Despite this, over the years there are several girls and the occasional boy feeling more comfortable talking to her than other teachers even before her authority expands. Those that come to her doorstep are heard out, referred to Pomona, given advice and sometimes chastisement. She adamantly stays out of their romantic entanglements so long as nobody comes to harm.
They used to say the last truly evil wizard was defeated and sent to Numengard before Minerva even got her Hogwarts letter. The falsehood of this aphorism becomes obvious not long after she is made Head of Gryffindor House.
With Voldemort on the rise, many of the girls she sees graduate marry young and have children right away. Some do it in an attempt to cling to the hope that they and their families will endure. The more pessimistic ones, she suspects, do it to leave a mark on the world while they still can. Minerva is just glad that they seem to listen to the lectures Pomona gives every few months and show enough sense not to get pregnant while at Hogwarts.
One of these promptly conceived babies saves the world.
In the following atmosphere of new beginnings she considers marriage for the first time in thirty years. When she causes a near scandal by keeping her maiden name she is almost fifty. Old for a first time mother but not too old, especially with access to Pomona for help. A tiny McGonagall is within her reach, or would be, if she wanted.
Maybe at one point, maybe if... but those thoughts are unfair to the man who is now her husband.
She is an aunt of five and a great-aunt of two. A widow after mere three years as a wife, she is glad that her instincts kept telling her no.
Her responsibilities are more than enough to keep her fulfilled.
The war flares up again. Despite the Orders’ efforts it becomes evident that they will not be able to keep the School safe, this time.
She sees it in the eyes of the women she meets during the summer after Dumbledore’s death and burial, the resentment that says that Minerva can be a formidable witch all she wants but she, unlike them, does not stand to lose a child or grandchild of her own.
When she allows her students to raise their wands and fight she does so on the grounds of a choice they all made. Individually. Together. Beneath the rush of adrenaline she is horribly afraid and immeasurably proud. They are hers.
She stands to lose all of them.