how to write a declaration in stamp paper

i am a student of Msc microbiology & my maternal uncle's daughter also student of Msc microbiology i.e. in relation sh3 is my sister at an university in Tamil Nadu...due to different problems in different parts of India my parents and also my maternal uncle's want that we stay together in a lodge or in paying guest rooms... but the authorities don't allow us..to stay in a room reason is that my surname is different with my sister's name...
Now the question is that how surname is going to be matched?? she is the daughter of my my Mother's brother..
so AUTHORITY want to give a declaration in stamp paper ..
how to write a declaration in stamp paper..and what to write??? please suggest me