A relative (we’ll call them “A”) may be reticent about certain aspects of their family history and not at all responsive to gentle or not-so-gentle attempts to ask certain questions. Other relatives may refuse to answer the same questions or indicate that they “know nothing.”
After A dies, others in the family may be willing to offer up details. A short time after a relative of mine passed, others in the family willingly shared stories about the family history I had never heard before–ever. It may be worth your time to revisit family members after another family member has passed. Wait a respectful amount of time to do it, but sometimes the informational floodgates open after one member of the family dies.