Most insurance companies do not cover common elective conditions for a period of 2 years.Very few have it for one year. All insurances have an pre determined list of exclusion or conditions that would not be covered in the initial period.
This is a 30 day waiting period and a specific waiting period. In 30 day period except trauma, all other will not be covered. The common ENT diseases NOT covered for 2 years would be mastoidectomy, tympanoplasty, sinus related disorders.
Some people think they are smart and add the disease on the pre-existing list, even in this case, many companies Do Not Cover until 48 month is over. For instance pleas see the religare(an insurance company) exclusion list. (https://cms.religarehealthinsurance.com/cms/public/uploads/download_center/standard-list-of-medical-exclusions.pdf).
To the best of my knowledge, insurance now in this context will be NOT BE HELPFUL FOR EAR SURGERY. You will have to go in for a self paid surgical package.
In the long run, the earlier we take medical insurance, the better it would be. Many companies offer a family floater policies. You can check further into Apollo Munich which might take a brother and sister as family. (http://www.apollomunichinsurance.com/insurance-articles/health-insurance/do-you-have-complete-family-coverage.aspx). Adding your names to parents insurance would be easier. Adding a sibling on a existing policy is not often possible.