Wikipedia
Valiathan is the surname used by members of certain families that are all part of a single original Tharavad and was a title corresponding to Unnithan. This latter title, originally known as Thankal, was conferred by the Rajah of Kayamkulam on Nair nobles of his state. In the 18th century it was Marthanda Varma of Travancore who conferred the title of Valiya Thankal (Senior Thankal) on the Vattaparambil family which was reduced to Valiathan. Correspondingly the other Thankals came to be known as Unni Thankals (Junior Thankals) or Unnithans.
The Vattaparambil family was originally based at Kayamkulam and served the Kayamkulam Rajah in various capacities as ministers, commanders etc. Also several princes of the Kayamkulam family had married ladies from this family. Sometime in the late 17th century due to some disaffection the Vattaparambil Thankals left Kayamkulam with a band of loyal Nairs and moved to a place called Keerikkadu. They constructed a fortress at this place and also, thus, came to be known as the Kottakkakathu family (Kotta in Malayalam means fort).
In the early 18th century Travancore was troubled by internal rife and the authority of the King was challenged by the Ettuveetil Pillamar. These nobles were opposed to an adoption made by the ruler in 1718 and out of fear for her life, the princess (who was the adopted sister of Marthanda Varma), was living in exile at Harippad with her four-year-old son (who grew up to be Dharma Raja). Although she was a member of the Travancore Royal Family, the princess was often pressed for money and resources. The senior most lady of the Vattaparambil family appeared to support the princess and her son and it was the little prince who first referred to her as Valiyamma (which was the term used to address one's mother's elder sister). Since then the senior most female of the Vattaparambil family was known as the Vataparambil Valiyamma.
In the year 1728 the princess received news that the Ettuveetil Pillamar had despatched a band of soldiers to assassinate her and the little prince. She decided to seek refuge with the Vanjipuzha Thampuran, the Brahmin Rajah of Chengannur, where she would be safe. In coordination with the princess's husband, the Kilimanoor Koil Thampuran, the Valiyamma provided an escort until Chengannur. She personally travelled with the princess and her presence of mind and the bravery of the Koil Thampuran helped save the lives of the princess and her son when they were ambushed at Budhanoor.
Years later in 1746 when the war between Travancore and Kayamkulam was at its height, Marthanda Varma sought the support of the Vattaparambil Thankals which was readily granted. The Kayamkulam Rajah was defeated and fled to Calicut but his officers continued with the battle and the son of the Vattaparambil Valiyamma was killed in battle. The story goes that Marthanda Varma himself came to Keerikkadu to console the Valiyamma and assured her that he would be like a son to her. The younger female members of the family thereafter were addressed with the title of Amma (mother) instead of the usual title of Kunjamma. The male members were addressed henceforward as Valiathans.
The Vattaparambil family had a sole female member in 1825. In 1859 she, being childless, with the permission of Maharani Gowri Parvati Bayi adopted the six members of the Thottathil Unnithan family of Pandalam. Three of these were women of whom one remained at Pandalam. The second lady went to Keerikkadu and settled therein. The third lady married the Rajah of Thiruvalla and settled there. These three families formed the three branches of the Vattaparambil family and are all known as Valiathans. The Valiyamma who had adopted them died in 1884 and the original lineage of the Vattaparambil family ended. However a record from 1883 shows the importance the family possessed more than a century after Marthanda Varma's times. The Valiyamma of Vattaparambil had made a representation to Maharajah Visakham Thirunal who issued an order as below: