First you should already knows, there are five major Tai Chi styles: Chen (陈式), Yang (楊式), Wu (吴式), Sun (孙式), and Wu (武式) or Hao Style, the Chen Style is the original style in Tai Chi , and the Sun Style is Youngest style among them all,
And we all know the story how Yanglu Chan Learned Tai Chi Chuan in Chen Village, In 1850 late Qing dynasty, Yang was hired by the Royal Family in China to teach Tai Chi to their Guards to Protect the Forbidden City, in training the people in Beijing and for the purpose of help elderly to excises for better health also aim to help Tai Chi the from the capital of China, the form was modify to fits or transfer to accept to people in all ages.
Yang Style was not the origin of Tai Chi, but Yang style was first to open to Public. First to spread in China.
Even now days, Chen Style was more hard to practice and not easy for old folks.