If a brahmin boy marries a NB girl, then also she gets transferred to the husband's gotra, by the mantras recited during the wedding function. The girl, therefore, becomes a brahmin. Hence, as long as the boy and the girl, the future couple abide by the brahmin ways of life and follow the religious customs, neither the boy who marries an NB girl, nor his father will lose any of their rights (lose any of the obligations) cast on them both as brahmins.
The only thing to ensure is that neither the boy nor the girl slip away from the brahmin way of life and take to non-brahmin customs
The only thing to ensure is that neither the boy nor the girl slip away from the brahmin way of life and take to non-brahmin customs