I believe LE just explained that a living sibling‘s DNA was part of the identification process. From that I infer that the siblings have likely known for weeks, if not months.
It’s interesting to consider, how might we as individuals each react to a situation such as this? If I were that living sibling … I think personally my desire for family privacy would be long since past, particularly if my parents were deceased. Actually … even if they were alive, I’d feel this way. I’d also be at this press conference. Physically.