Reports said the 21-year-old was in a group whose loud partying at a Birmingham hotel angered fellow guests in the early hours of Sunday morning.
Xia sent a direct Tweet to Grealish: “As I said b4, focus every minute on&off pitch, choose the right type of ppl 2be with.Don’t let ppl who trust u down!”
Xia added: “It’s not warning but just elder brother’s talk. I trust jack can really learn and be a MAN! Don’t go wrong direction.”
Grealish has scored two goals in eight appearances so far this season.