If you grant a trusted family member like your child or wife or husband knowledge to your wallet details is same as granting them access to the prompts into your wallet. Nothing different about that. Well, you don't wish to see it as a risk but it still doesn't take the fact away that we have allowed a third party access to our wallet even though it's a family member we trust. Humans do change and are unpredictable in the next moment about what circumstances can make them do or not. However, we can't help but to have someone we can trust in securing our funds in our abrupt absence.
I'm referring to knowledge about Bitcoin, i can teach any relation about Bitcoin and wallets but wouldn't give them access to my keys or seed phrases. Like our fathers do back then, there is always a case where private notes are kept including documents that is only accessible to the parent at most the head of the family, since my keys can go in written form it will be stored in that case. If unfortunately life becomes unfair after sudden passing, that relation knows about the case and how to retrieve those documents or notes. Humans change but if out of all relations not a single person is trust worthy to keep secretes then there is no need of setting up Bitcoin inheritance.