Sorry to hear about it.. although your's is a different situation as your biological father had passed away.
Children from broken homes often face these problem when parents divorce and / or mother remarries and name of the child is changed... there is Identity Crises.. the identity of the child is lost..
There are procedures for name change..
you can file for name change through Govt Gazette.. you will have to give a declaration on affidavit.. and also give advt in the local news paper mentioning your new name has now been changed from (old name)_____ to (new name)________
If you want to change your name, you need to send a request letter to your State Government for Publication of Name Change Notice in Official Gazette. Here is the sample letter to help you to do so.
To
The Under Secretary to Govt.
Department of Commerce & Transport (Commerce)
_________________, ______________ (State)
Sub (Publication of Notice in Extraordinary ___________ (State Name) Gazette for Change of Name)
Sir,
With due respect I want to State before you that I have changed my name _________________ (old name) to _________________ (new name) by virtue of an affidavit made before the Notary Public, _____________ (Place) on _____________ (date), which have also been published in the daily _____________________ (Newspaper Name).
Now I want to publish the Notice in Extraordinary issue of ____________ (state) Gazette and therefore I request you to issue necessary orders for the publication of the same in E.O.G and obliged.
Required documents are attached herewith for ready reference:
1. Original Newspaper
2. 2 attached Xerox copies of Affidavit regarding change of name
3. 2 copies of DTP of Notice
4. 2 deed changing Surname Forms
You’re faithfully,
Name
Address
(Form and Guidelines for the same are attached herewith for your kind perusal. You can also take the help of an advocate.)