Adoption Process within a Family

Hello All, I am planning to adopt the child who belongs to my sister (Intra family Adoption). Before I ask questions I would like to give a brief about the situation. My sister and her husband got divorced 14 years back and since then her son is with us (Son was 6 month old when he came to us). As per their divorce deed my ex brother in law can take his son back after child completes his 10th standard education. During this 14 years period my sister and ex brother in law get married and started their own family life respectively. Recently I contacted the ex brother in law and sister for adoption as I am facing a couple of society & legal challenges to be a guardian of sisters child. Finally both are agreed and shows the positive response for adoption. After this I started looking for correct procedure to adopt the child and I kept reading more and more I started getting confused about correct procedure of adoption. Some says that adoption deed to be made and registered, some are saying its not necessary to register the deed and some says that I need a court order for adoption. I request you all to guide me the correct family adoption procedure. Thank you very much in advance, your inputs will be really valuable to me.