A quick timeline.
As we've been hopping all over the timeline recently, I just wanted to lay out the order of events, as I understand them (with an obvious focus on Salazar). This is just for future, easy reference.
*The four meet and eventually decide to open a school of magic.
*As preparations are being done, they clash re: what sort of students should be allowed. Salazar is eventually overruled.
*He still believes himself to be wholly in the right and plans for a time when Hogwarts might be cleansed; as the school is being built, he secretly includes the Chamber.
*The school opens. Salazar is falling more and more in love with Rowena; he often thinks about acting on these feelings and asking her to marry him.
*A few years into the school's life, Salazar finds himself in a corner: his brother has died and thus their family lands are up in the air. By his dead father's will, only a married man may hold onto the lands, which have been in their family for centuries. In order to protect his family's name and their serfs, he marries the daughter of the nearest (MAGICAL) land-holding lord, thus expanding his own lands. He does not love her, but they get along.
*Some time after that, Salazar and Rowena make a mistake, but one they don't regret: they start an affair.
*Rowena becomes pregnant. Clearly there's going to be a lot of issues with this.
*Things start to become more and more rocky between Salazar and the other three Founders: he lashes out more regularly because of the stress in his personal life. He begins to refuse to teach any non-Pureblooded students and, actually, starts to send his own children to other schools. Eventually, thirteen or so years after Helena is born, Salazar leaves Hogwarts.
*The four meet and eventually decide to open a school of magic.
*As preparations are being done, they clash re: what sort of students should be allowed. Salazar is eventually overruled.
*He still believes himself to be wholly in the right and plans for a time when Hogwarts might be cleansed; as the school is being built, he secretly includes the Chamber.
*The school opens. Salazar is falling more and more in love with Rowena; he often thinks about acting on these feelings and asking her to marry him.
*A few years into the school's life, Salazar finds himself in a corner: his brother has died and thus their family lands are up in the air. By his dead father's will, only a married man may hold onto the lands, which have been in their family for centuries. In order to protect his family's name and their serfs, he marries the daughter of the nearest (MAGICAL) land-holding lord, thus expanding his own lands. He does not love her, but they get along.
*Some time after that, Salazar and Rowena make a mistake, but one they don't regret: they start an affair.
*Rowena becomes pregnant. Clearly there's going to be a lot of issues with this.
*Things start to become more and more rocky between Salazar and the other three Founders: he lashes out more regularly because of the stress in his personal life. He begins to refuse to teach any non-Pureblooded students and, actually, starts to send his own children to other schools. Eventually, thirteen or so years after Helena is born, Salazar leaves Hogwarts.