Is there any risk to marry a girl with the same surname?
There is no contraindication for marriage within the same surname. What is more important is the relationship between the two families and the history of any genetic disorder in the families. There are several subcastes in India which marry in the same surname eg. Bhargavas, Chaturvedis, Mathurs, Rastogis, etc. For further advice, information on the above two aspects would be necessary.