Welcome to Spotify Community and thanks for reaching out here!
First of all, super sorry for your loss and I hope you don't mind I'm answering in English.
In this case, if you have access to the manager account, you can cancel the Family plan on their account and start a new one through your own account. If you don't have access to their account anymore, you and the other dependents can get out of the Family plan on your account overview page. After getting out of the Family plan, you can start your own subscription and then invite the other members as your dependents. You can get more information about it here:
If you have further questions or if you need anything else, let me know! I'd love to help!
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Note: I'm not a Spotify employee.