Microsoft 365 Family grants Office 365 suite to yourself and up to 5 family members (under that single license), that being the click to run office installed product as well as the online versions and a 1TB Onedrive per family member.
Where as the M365 Business SKUs, users are individually licensed and have access to additional features besides the office suite depending on the extact license SKU but typically include business email, teams, sharepoint etc, with the Business Premium containing Intune and Azure information protection see Compare All Microsoft 365 Plans | Microsoft
So to answer your quest do you need both - that depends, if you are sharing your M365 family subscription with other family members, then yes you need to keep this, as the M365 business licenses are per user. if you are using the features of the business license (e.g. exchange, sharepoint etc) then you need to keep the business license.
If you are only using the office applications (word, excel, outlook etc) and none of the other functionality of the Business SKU then in that case keeping the M365 Family and cancelling the Business license would make most sense