Do I need a Invitation Letter

I am a American citizen and my Wife is a China citizen and she also has a permanent Residential Card. We have travel to and fronm China for the past 7 years and I have not had to obtain a "Invitation Letter" before. We usually go to visit her family during the Festival season or special family gatthering like weddings.

She informed me that now I have to obtain a "Invitation Lette" in order to obtain a Visa for my trip I am planning this coming January. Is this True?