OP, First of all marrying in same gotras is prohibited per say becoz it means the said people are from same bloodline. Meaning siblings. Nowadays if you are not related by blood , even that is considered becoz of dearth of good matches.This relation you are describing is marriage based and not by blood relation. You can go ahead if that person is good in all aspects.Nowadays rarely you get a good match with subcaste and everything falling into place. So let go of that as criteria. You need a good match in all other ways that's it.My hubby;s family and ours are not of same subcaste but neither found it objectionable. Go ahead this is not a relation in any sense. You are thinking too much . Go ahead . Good Luck.