as long as the person invited can provide the strong tie/relationship between the two persons and how important it is for the uncle to be present at your son's gratduation ceremony. Past pictures and letters can be shown to the visa officer for proof. The uncle should also present to the visa officer his employee information in CHina (it could be a employment contract or a letter from employer), monthly income,any saving and checking accounts, ownership of real estates, etc. and other ties in CHina that will prevent him from staying in US and not going back. In short, the Uncle need to show that:1. It is important for him to present at your son's graduation ceremony; 2. the Uncle or whoever is going to pay the expenses has enough money for the trip; 3. the Uncle will go back to China after the ceremony. Information needs to be REAL! Hope this helps.