Purchase of a house

Dear sir, Am planning to purchase a house from Mr.Ravi aged 58 years (in Tirupathi) who purchased this house in 2004 from his own earned money. This house is in the his name. Mr.Ravi has two sons and one daughter all are majors and married. Now Mr. Ravi who is real owner of this house and his sons are willing to come to registration office and sign the sale deed except his daughter. My doubt is 1. Is required to sign his daughter also ? 2. If his daughter doesn't come and sign, will have any legal issues in future ? or 3. Mr. Ravi alone is enough for registration as this property is purchased in his own hard earned money ? Pls suggest on this sirs.