We met 6 months after his wife died of pancreatic cancer. To be honest when he told me he had just lost his wife I wanted nothing to do with him, but he was persistant. My dad's family embraced my mother and welcomed her into the family, as did my brother's mother's family. My mom and dad stayed married until in death they did part, 45 years later. He loved her, and she was a part of his life, and she will always remain a part of him.
Similarly, he should not hide you from his in-laws, or from anyone else in his life, if he is really serious about having a future with you, and you should address that with him.
On occasions when he makes no mention of his late wife, you and your widower have a great time together. Men who haven't quite reached the ready-to-date stage nevertheless manage to draw companions into their trajectory while they figure things out.
He loves the attention you lavish on him and he tries to reciprocate. Some women spend years orbiting a world of grief that is not their own.
Someone who is in the midst of the grief process cannot be fully present with you and emotionally available for a relationship.
Communicate openly with him about his emotional state. If he seems not to have grieved much, consider that a red flag.