Ok so this all happens about 4 years after Harry, Ron, Hermione & Ginny all graduate from Hogwarts.
First the story of Harry & Ginny:
Well as we all know Ginny is younger then Harry, but did that stop him from marrying his true love. I think not about a year after Ginny graduated, her and Harry went on a long vacation. This vacation lasted about 4 months, when they were to return Ginny and Harry were officially Mr.& Mrs. Harry Potter. The whole family was shocked. But the marriage had made no difference to Harry or the Weasley's because he had always felt like family to the them. To the family's surprise Harry & Ginny were expecting their first child which was to be named nothing other then Sirius James Potter.
Now on to the story of Ron & Hermione:
Hermione and Ron both graduated from Hogwarts with flying colors, they were so in love; So they thought. They later got engaged but that did not last. Ron had a change of heart he was not ready for that type of commitment. The two took some time off from each other. Then Ron had realized that Hermione was everything to him and that he needed to come up with a way to win her back. As a matter of a fact he did, on her birthday he stood outside the window of her apartment with a bouquet of flowers and sarinated the square with candles playing her favorite song. They fell back in love and were closer then ever and as Ginny and Harry got married and had a baby Albus Weasley.