If they were identical twins, the two would be a lot more similar. It's one sperm and one egg that combine, and after the first split, each splits independently into adults.
As for the character of the two, feng shui, the east palace belongs to the eldest son, it is recommended that the child live in the house off the east side of the bedroom, if not, the bed is placed in the east position of the room. Daughter try to live in the west side of the room.
Additionally, in daily life, the sister may be too good, the son unconsciously be influenced, and then imitated, it appears to be feminized. Some families do not have daughters, and the mother is excellent or strong, it will also be like this. Suggest more encouragement, affirmation of the son, let him take the lead in making decisions, establish the status of the eldest son in the family. For example, outings, meals, trips. All the planning. The decoration of the home, the reception of guests....
If available, you can choose to let him live in school, separate from his sister, with male students, slowly influence.