Unchained offers a DIY package where they've prepared basic guidance, but you'll need to do the legwork on the appropriate steps for title transfer and key succession. A checklist is included to walk you through the process. This also comes with their more expensive hand-holding concierge onboarding.
https://unchained.com/blog/unchained-inheritance-protocol/
https://unchained.com/product-pricing?tab=inheritance-pricing
Note: I have not personally reviewed the contents of the package and cannot attest to its thoroughness or suitability for your jurisdiction. For just getting started with multisig and collaborative custody providers, I wrote about both Casa and Unchained in the past. These have been open sourced and available at the following which includes screenshots so you know what your getting into before KYCing for an account
https://github.com/vicariousdrama/howto/blob/main/bitcoin/multi-signature-bitcoin-with-unchained-capital.md
https://github.com/vicariousdrama/howto/blob/main/bitcoin/multi-signature-bitcoin-with-casa-keymaster.md
Hope this helps.