Partition disputes

Hi I have purchased a property from Mr x in 2013, it was a built house and had corporation khata in x name in bangalore city. Currently paying house loan EMI and had all the legal documents and bank loan taken Mr x purchased from Mr y in 2005. Mr y purchased from Mr z in 1995. Mr z purchased site from Mr A in 1980, later Bangalore development authority resold it to Mr z by giving possession certificate. BDA commissioner signed sale deed to Mr z. In 1970 Mr. C purchased property, and Mr. C died inter state in 1974 leaving behind 4 boys & 3 girls (2 boys were major and 2 were minors), in the same sale deed, 2 Sons (Major) who sold this property clearly mentioned the minor names and to take care of the minors they are selling the property. From 1974, it has changed several hands. Now suddenly a person Mr B (minor son during 1974) files a case and gives notices to Mr x and Mr y along with his brothers and sisters 6 of them. He is now 48 yrs old, he might be 6 yrs old when his brothers sold their property in 1974. Mr B is saying he has not signed documents in 1974 and he demanding 1/7th share of the property. Can Mr. B has rights now after 42 years of the transaction? He has become major in 1986 (30 years over after he came major).. pls advice.