Short Answer 
To resolve the issue of not being able to accept a family invite on Steam, first understand the problem may be related to family sharing policies. Next, gather relevant information like your account details and the error message, then contact Steam Support with this information to receive assistance.
Step 1: Understand the Issue
The first step is to comprehend why you are unable to accept the family invite. The error message suggests that Steam’s system does not identify you as part of the same household as the other family members. This issue usually stems from Steam’s family sharing and household verification policies.
Step 2: Prepare to Contact Support
Before reaching out to Steam Support, gather necessary information that may help expedite the process. You might need to include:
- Your Steam account details
- The error message you received
- Details about the family members you’re trying to share with
Having this information organized will assist support representatives in providing you with the best help possible.
Step 3: Reach Out to Steam Support
The final step is to contact Steam Support for assistance. You can do this by submitting a support ticket or using their live chat option. Clearly explain your situation and include the information you’ve gathered to streamline the resolution process. Steam Support is equipped to offer specific guidance or fix any account issues preventing you from joining the family.