Blackstone Group Inc. acquired a majority stake in Ancestry.com Inc., the business known for family history research and DNA testing. The deal is valued at $4.7 billion, Blackstone said in a statement Wednesday. It’s the first acquisition by Blackstone’s largest ever private equity fund. Silver Lake and Singaporean sovereign-wealth fund GIC Pte have been the majority owners since 2016. After the deal closes, Blackstone will own about 75% and GIC will still hold about 25% of Ancestry.com, said people familiar with the matter, who asked not to be identified because the information is private.