Languages similar to or like Maithili language

Indo-Aryan language spoken in northern-eastern India and the Terai region of Nepal. One of the fastest growing languages in the world according to People's Linguistic Survey of India. Wikipedia

Language spoken primarily in the Anga region of Bihar and Jharkhand states of India. Also spoken in some parts of the Terai region of Nepal. Wikipedia

Eastern Hindi language of the Indo-Aryan branch spoken in northern India. Primarily spoken in the Awadh region of present-day Uttar Pradesh, India. Wikipedia

Subgroup of the Indo-Aryan languages that is usually included in the Eastern branch of Indo-Aryan. The Bihari languages are mainly spoken in the Indian states of Bihar, Jharkhand, West Bengal and Uttar Pradesh and also in Nepal. Wikipedia

Linguistic region encompassing parts of northern, central, eastern and western India where various Central Indo-Aryan languages subsumed under the term 'Hindi' are spoken. Sometimes also used to refer to nine Indian states whose official language is Standard Hindi, namely Bihar, Chhattisgarh, Haryana, Himachal Pradesh, Jharkhand, Madhya Pradesh, Rajasthan, Uttar Pradesh, Uttarakhand and the union territory of Chandigarh and the National Capital Territory of Delhi. Wikipedia

Eastern Indo-Aryan language spoken in the Indian states of Jharkhand, Bihar, Chhattisgarh and Odisha. Native language of the Sadan. Wikipedia