Marriage between same surnames

There is no legal hurdle in the marriage if only surnames are same. The parties should not be within prohibited degrees of relationships. You can go ahead with the marriage.

Yes, you can marry any girl having any surname or gotra, legally,  if she does not fall under prohibited degree of relationship for marriage with you.

There is no restriction in the name or surname for marriage.  The restriction to marry is that the bride and groom should not fall within the prohibitory relationship wherein the marriage will be considered as void.

Dear Sir,
I hail from south India. My sister recently informed me that she loves a guy.The problem is that he has the same initial and same gothra as us. He even says that he is from the same village as us,but since his father expired he has moved to another town.In our region same initial marriage is highly prohibited. Also ours being a small village there is a high chance that we have the same ancestor. But my sister is totally in his charm is not listening to reason.She says he has promised to change his surname before marriage.
Please clarify if this marriage is legal under the Hindu Marriage Act?Also can some one change their surname?

Do not guess that they are in prohibited relationship.  Find out this fact whether they have common ancestor and also fall within the prohibited relationship.  Further, as you are in South India, you also find out such marriages are valid as per customs or not, even though they fall within the prohibited relationship.  Because, in some of the South Indian States, such marriages are totally valid and protected by legal provisions.  Without finding the fact, do not try to break the heart of your sister.  If you fail to find out all these facts, then let them marry, otherwise if they are suitable.

See first of all same surname or same initial and things of that sort may create caste  customary restrictions leading to uncomfortable and embarrassing situations to communal harmony within the region, but it is not illegal as per law. Therefore until the relationship does not falls within the prohibited or sapinda relationship, there is no legal infirmity in your sister marrying the proposed person.  These days when inter caste or inter religion marriages are on the high spree, do you still confine yourself to medieval age practices?  Come out of the circle and see what the world outside the circle is.

Our family has no problem with inter caste marriage.As I have stated people having  same surname and same gothra are considered brothers in our region (A.P). We live in a small town. So their children will have a big problem with the relations with in the family. SO our next course of action is to find out whether they have the sapinda relationship?