They initially ruled as feudatories of the Western Chalukyas and around the middle of the 12th. century, declared their independence. At their peak under Singhana II, they ruled a large kingdom stretching from the Tungabhadra to the Narmada rivers.
Who are these rulers has been of considerable debate between Scholars, Whether they are Yadavas or Marathi or Kannada stock. let us see.
Yadava
The Suena dynasty claimed descent from the Chandravanshi Yadavas of north India. According to the verse 21 of Vratakhand (a Sanskrit work by Hemadri), the Seunas were originally from Mathura and later moved to Dwaraka. Hemdari calls them as Krishnakulotpanna (i.e. descendants of Lord Krishna). The Marathi saint Dnyaneshwar describes them as yadukulvansh tilak as well. Some of their inscriptions call them Dvaravatipuravaradhishvaras ("masters of Dvaravati or Dwaraka").
A stone inscription found at Anjaneri near Nasik says there was a minor branch of the Yadava family ruling over a small district with Anjaneri as the chief city. The inscription indicates that a ruler called Seunadeva belonging to Yadava family called himself Mahasamanta and made a grant to a Jain temple.
Dr.Kolarkar also believe that Yadavas belonged to North India.
Marathi
Prof. George Moraes, V. K. Rajwade, C. V. Vaidya, Dr. A.S. Altekar, Dr. D.R. Bhandarkar, and J. Duncan M. Derrett, the Seuna dynasty rulers were of Maratha descent. The Seunas patronised the Marathi language. Digambar Balkrishna Mokashi noted that Yadava dynasty rule was "what seems to be the first true Maratha empire". In his book Medieval India, C.V.Vaidya states that Yadavas are "definitely pure Maratha Kshatriyas".
Dr. O. P. Varma, state that Yadavas themselves were Marathi speakers and the age of the Yadavas.
The Yadavas of Devagiri patronised Marathi and Marathi was their court language. It is said that Kannada might be a court language during Seunachandra's rule,however Marathi language was the only court-language of Ramchandra and Mahadeva Yadavas. The Yadava capital Devagiri became a beacon for learned scholars in Marathi to showcase and find patronage for their skills. The origin and growth of Marathi literature is directly linked with rise of Yadava dynasty.
Kannadiga
C M Kulkarni, Colin Masica, Shrinivas Ritti etc. believe that the Seuna Yadavas were Kannada-speaking people. Linguist Colin Masica believes that the Yadavas were originally Kannada-speaking and used Kannada in their inscriptions (along with Sanskrit). However, by the time of Muslim conquest, they had begin to patronize Marathi, and Marathi phrases or lines were beginning to appear in their inscriptions. Dr. Shrinivas Ritti's speculates that Seunas must have been originally from Kannada-speaking region and migrated northwords due to political situation in the Deccan at that time
Many Seuna rulers had pure Kannada names and titles like "Dhadiyappa", "Bhillama", "Rajugi", "Vadugi" and "Vasugi", "Kaliya Ballala". Other kings had names like "Singhana" and "Mallugi" which were also used by the Southern Kalachuri dynasty. Records show that one of the early rulers "Seunachandra II" had a Kannada title Sellavidega. The Seunas had very close matrimonial relationships with royal Kannada families through out their rule . Bhillama II was married to Lachchiyavve from a Rashtrakuta descendant family in Karnataka area. Vaddiga was married to Vaddiyavve, daughter of Rashtrakuta chieften Dhorappa. Wives of Vesugi and Bhillama III were Chalukya princess.
Also, over five hundred inscriptions belonging to the Seuna dynasty have been found in Karnataka, the oldest being of the rule of Bhillama II. Most of these are in Kannada language. some others are in Kannada language but Devanagari script . The Seuna coins from the early part of the rule itself have Kannada legends. Many scholars such as Dr. O. P. Varma, therefore believe that Kannada was certainly a court language along with Marathi and Sanskrit during Seuna times.
During the rule of the Seunas, ruling chieftains who were related to the Seuna Kings were from Kannada-speaking families, like the Seunas of Masavadi-140 in present day Dharwad. Dr. A. V. Narasimha Murthy opined that during the later part of the Rashtrakuta rule from Manyakheta, Seuna chieftains were despatched from the Karnataka region to rule near Nasik.
Kannada was one of the court languages since early Seuna times, as is evident from a number of Kannada-language inscriptions. Kamalabhava, patronised by Bhillama V wrote Santhishwarapurana, Achanna composed Varadhamanapurana in 1198, Amugideva composed many Vachanas or devotional songs. He was patronised by Singhana II. Chaundarasa of Pandharapur wrote Dashakumara Charite.
Eventhough Marathi Scholars claim ,Marathi was the only court language
in Ramachandra and subsequent Seunas rulers period, there are abundant
kannada inscriptions in Maharastra, Karnataka and Andhra.
Conclusion
It is common for rulers to claim alligence to historical characters in the past, especially in karnataka as it they followed Manu philosophy to get a divine right to rule. So all the rulers since Maurys have claimed to belong to some divine castes to differeniate themselves from the people they ruled. So calling themselves to be yadavas from north should not be taken seriously unless there is evidence for that. Here there is no evidence.
Seuna rule saw the development of Marathi, and it was the golden age of Marathi. That should not make them blind to Kannada origin, Kannada rulers have ruled all over India have patronised the local language everywhere Telugu (Chalukyas, Vijaynagar, Rastrakuta), Tamil (Gangas, Chalukya, Rastrakuta), Gujarathi( Chalukya, Solanki), Bengali (Pala, Sena), Oriya(Ganga), Nepali(Malla) and various prakrits in present day Rajasthan, MP, UP , Bihar by , satavahana and subsequent Rastrakuta rulers like Rathores(Rathod). And partronising the local language has given a edge to the kannada rulers in a alien territory.
Around 10th century Kannada was the predominant language in Maharastra should not be missed.
So the seunas are kannada origin