Originally posted on this thread at the Dancing Dove message board.
I have omitted notes where I suspect there to be canon I can't recall. Anyone willing can reply with additions, which will be edited into this post if relevant.
Leon of Naxen: Gareth the Elder and Lianne's father. Was known, in his lifetime, as a towering, bald man with a significant black beard and dark, imposing eyes.
Annabella of Sancia: Gareth the Elder and Lianne's mother, hailing from a Tyran noble house and, in fact, the niece of the Tyran ambassador to Tortall, at the time, who was quite scandalized when his brother's daughter was briefly and successfully pursued by a knight easily ten years her senior. Posessed of the notable Tyran dark beauty.
Gareth I of Naxen: The Duke G we all know and love. To my recollection, he is tall and thin, with brown hair and eyes. Was almost genetically scandalized when his baby sister, two years his junior, announced she was in love with his best friend, Prince Roald, and intended to marry him whether Papa approved, or not.
Lianne of Naxen (later of Conté): Roald's queen and Jonathan's mother. Again, I vaguelly remember Jon getting the black hair from her, although I might have made this up. In my mind, she is tall and thin, like her brother, with very black hair, deep brown eyes and an almost olive complexion.
Idenna of Aili (later of Naxen): Decided she would marry Gareth I within six hours of meeting him and then got her way, to no one's surprise, least of all her father, who raised her and her three brothers almost entirely alone. I've a vague impression of wildly curly chestnut hair that refuses to go gray, an almost waxy complexion and pale, piercing gray eyes.
Gareth II of Naxen: "We're naming him after you, dear, because at this rate, you will work yourself to death before the poor boy has even met you. There's really no use arguing, you know". The rest is histo -- err, canon.
Cythera of Elden (later of Naxen): Quasi-canon proclaims her sweet, curly, ash-blonde, and blue-eyed. I see no sense in arguing, except to say she really likes wearing white linen, much better than any other cloth.
Alexandra of Naxen: Gary and Cyth's first, born a year after Alanna's twins, named after an errant friend and usually called Lexa. Her skin, eyes and the curliness of her hair are from her mother, but she has her father's brown hair. My initial writeup said she was "not unlike a female version of Elijah-Frodo", so I'll stick with that.
Frances of Naxen: Born four years after Lexa, named after a prematurely deceased friend. Initial writeup says she "looks a lot like Gary, except shorter: light brown skin, brown hair cut short, brown eyes, a little on the stocky side". I think she may have the Naxen Gift, probably a strong yellow color.
Gareth III of Naxen: Has unanimously been named Gareth Nathaniel, or Gnat. It just.... fits. According to quasi-canon, he was born the year Kel started training, meaning three years after Frances. I was content to have both girls be brunettes, and wanted Cyth to leave a phenotypal mark, so Gnat "has his mother's curly blonde hair and fair skin, also fairly stocky, with brown eyes".
As a final, irrelevant note, Lianne of Conté, Jon's daughter, I wrote as resembling her namesake. Because I was sick of all those freakin' blue-eyed Contés.