There could be many ... depends on your current situation. You can tell 1. I am getting married (if you are unmarried) so would like to have my parents here. 2. We are expecting child (if you are married and your wife is pregnant) 3. We have greatest Hindu festival in OCT ... so would like to have them here. 4. Their health condition is no good enough for travel (if they are sick and have problem travelling) 5. I will be going back in few months and would like to travel together .... and list goes on of course u may require supporting documents for what ever you say.