I'm a USC and wish to apply for my Dad & my (married) Sister (and her family - kids ages 10 & 14.) While the GC process for them is in progress (I haven't filed yet), will they be able to visit US? My Dad already has a visitor visa but not my sister and her family. With the time it takes for sibling, do you think it would create a problem for her sons (if they decide to come to US for higher studies in the meantime?) What would be recommended?