Chil marriage

Hello, It's a question about my friend. His name is Arun. His grand father arranged his marriage in age of 12 in year 1996 with a girl age of 10 approximately. After that girl didn't come to Arun 's home ever. After completing age of 18, Arun 's family told him that he is married. His family went to girl's home to take her in Arun 's home but girl's family and girl both refused to come by saying that he is ugly and that marriage has no means. In age of 27 Arun got job in government bank while girl's boy friend left her. Arun meet another girl sashi and start loving her. Now arun wants to marry Shashi so he told their family. His family said that due ritual in village he has to be annulled with his wife whom he had been married in age of 12. So his family went to girl's home for ritual but this time girl's family refused and said that arun is married with their daughter and he has to come take their girl or give them 5 lakh rupee for their daughter. I want to kNow that Arun child marriage is valid ??? Now Arun is 32. After marriage Arun never meet that girl neither he has any memory about his marriage???At present Arun can marry Shashi legally???