((Okay I am taking my best wack at the answer to the question, if I am wrong please tell me XD))
Kiara nodded, " Professor Dumbledor was the Secret Keeper of Grimmauld Place, after he died Grimmauld Place no longer had a Secret keeper, and the owner of the House, Sirius Black died Owner ship went to the remaining relatives, who were death eaters. After a while yes the people who knew where it was to begin with were able to enter the house, they just couldn't tell anyone else" she explained.