my brother's visa

Good morning...
My husband is Chinese and we are currently living here in China.
Last Dec 2014, my husband invited my brother to visit PRC and my brother was granted an S2 type as we were told that S2 type is extendable. My brother's S2 was extended for 2 times which allow him to stay PRC for a year without exit. His S2 type is going to expire this coming Dec 2015. He is going back to Philippines and is planning to visit again. Is he allowed to enter PRC this January 2016? Because someone said that my brother will have to wait for 6 months before he can enter. Is it true?
Thank you and hoping for your response.