It is not clearly known in which year Fred Weasley II and Roxanne Weasley were born. However, it is believed that Fred Weasley II is the elder brother of Roxanne Weasley, and it is also claimed that Victoire Weasley is the eldest of the Weasley cousins. Since Victoire was born in 2000, it is likely that all the other Weasley cousins were born after 2000 or in 2000. Fred and Roxanne are most likely to be born after 2000 because Victoire's parents, Bill and Fleur, got married in 1997, way before the other Weasley siblings.