Unless you know the Apple ID and Apple ID Password your family member used, you cannot get in the iPad yourself.
If all you want is to be able to use the iPad and you don't want any of the data on the device, you can take a copy of the death certificate, a letter from the estate granting you ownership rights and if at all possible the original purchase receipt to Apple and they may be willing to erase the device for you to use.
If you want to access any of the data on the device, such as cherished family photos, this link will detail what Apple will require for that --> How to request access to a deceased family member's Apple accounts - Apple Support
If you don't want any of the data, just use the advice I provided above.