Spoilers: Sylvain is introduced in Yuuri's Hot Date.
AKA: Squire Sylvain von Tarkenburg, Sylvain Lord Donaghie, the Tark.
Age: 104 (110 during YHD)
Looks: ~5'9", pleasant but unremarkable blue-eyed blond.
Character: Prize! Sylvain loves kids, is socially gifted, charming, genuinely kind and warm. Smart, well-educated, well-spoken.
Special skills: Charisma, business acumen, economics, political savvy.
Family: Groomed as heir to the powerful and vastly wealthy von Tarkenburg squires of Bielenfeld. When we meet him, aged 110, his grandfather had recently (within the last 20 years) inherited the Top Tark spot from his great-grandfather. Sylvain's father Soujourn von Tarkenburg is the current heir. His mother's name is Evrinne.
Sylvain became Lord Donaghie during YHD. He's betrothed to Kieran von Donaghie.
Other: Like many nobles, Sylvain lived at Castle Bielenfeld while pursuing his nobility degree. His father and Aldrich von Bielenfeld are of an age, and close friends, and had no doubt been plotting Sylvain's takeover of Donaghie for years. Sylvain's tight with all the von Bielenfelds.
At this point, Sylvain has a grand adventure ahead, turning around the economically beleaguered domain of Donaghie.