1) no formal deed of adoption has been made
2) there has been no giving and taking ceremony wherein your parents gave you in adoption to your adopted mother
3) your adopted mother died intestate ie without a will
4) on her demise her property would devolve on her siblings unless you are able to prove a valid adoption
5) in the event any legal proceedings are taken by her other legal heirs oppose it on ground that the deceased had adopted you as her son
6) you have not mentioned whether your birth certificate , school leaving certificate , ration card and other documents reflect her name as mother