As indicated earlier Venus and Moon conjunction in the 12th house makes a person sexually active and therefore he will have interest in girls etc. I feel you should not be a teacher at home rather a friend, because you are not his teacher. As a sister I know you have a responsibility and I know you could do a better job by being a friend and not like a teacher.
Therefore leave him alone for the moment. Do the remedies as indicated and changes of love marriage are indicated and when the time comes just support him rather than suppress him.