Our answer: she is Mandi Gosling, the actor's sister. (We should've seen this coming, honestly, because Gosling's La La Land partner-in-crime, Emma Stone, also brought her sibling. These two seem to be cut from the same star quality cloth.) A quick reverse Google search led us to hard, internet proof that the guy has a blonde sister — and she's definitely the woman sitting with him at the Oscars. Gosling's elder sister, Mandi is pretty internet elusive. According to an Imdb profile, she was an associate producer Dateline, but it's possible this is a different Mandi Gosling. Mandi did not walk the red carpet with her brother, so she did not appear in pre-ceremony interviews.