I can say that Yad Vashem's database is actually sorely lacking. Their website is very difficult to search.
In my own family, my great-aunts filled out a Page of Testimony for their sister and brother. Their brother's page includes 4 children written in the sidelines and Yad Vashem only lists 3 of them, missing one that's written, and their sister's page leaves out her 1 year old son, so he's still missing. And they never filled out a page on their mother, or I can't find it, so in my own immediate family, the records are missing 3 people.
In my own family, my great-aunts filled out a Page of Testimony for their sister and brother. Their brother's page includes 4 children written in the sidelines and Yad Vashem only lists 3 of them, missing one that's written, and their sister's page leaves out her 1 year old son, so he's still missing. And they never filled out a page on their mother, or I can't find it, so in my own immediate family, the records are missing 3 people.