How to get Nepal Citizenship ?

Hey guys, i turned 21 years old, i was born and bred in india, but my parents and my whole ancestry is from nepal, my parents came to india in around 1996 and since living here and we are settled here, but now my parents want to move back and want to settle there, my father have nepal citizenship but my mother, me and my siblings doesn’t have any documents of nepal. I am writing this of hoping if anyone of you will guide me through this and also i will share every details with you here. Thankyou.