My wife, who is a permanent resident, wants to bring her adult son with wife and new grandson to visit us in the USA. Her son already has a 10 year Visa and used it about 4 years ago to visit us in the USA before he was married. His wife has no Visa. I sent a letter of sponsorship for him at the time, but have no way of knowing if it had any influence on the decision to issue his Visa.
My question is, what is the best way I can help his wife and infant son get a Visa also, so they can all come to visit? Should I write another sponsorship letter for her?