Hello Galalon9,
Thank you for using Apple Support Communities.
I understand that you are having issues inviting your brother to join your Family Sharing group and/or with his joining your group. Take a look at the following support article that describes the setting up of Family Sharing.
Set up Family Sharing
Here are the relevant sections for inviting/joining a group. You will want to make sure that these steps were followed and nothing was skipped preventing your brother joining.
As long as you're both using iOS 8 and later or OS X Yosemite and later, you can add anyone who has an Apple ID to your family. If you have children, use these steps to create their Apple ID and add them to your group. Use the steps below to add someone who already has an Apple ID.
On your iPhone, iPad, or iPod touch:
- Go to Settings > [your name] > Family Sharing. If you're using iOS 10.2 or earlier, go to Settings > iCloud > Family.
- Tap Add Family Member.
- Enter your family member's name or email address and follow the onscreen instructions.
- If you’re using iOS 11 or later, choose whether you’d like to send an invitation via Messages or to invite them in person. Then follow the onscreen instructions.
On your Mac:
- Choose Apple menu > System Preferences, then click iCloud.
- Click Manage Family.
- Click +, then follow the onscreen instructions.
If your family member is with you, they can enter their Apple ID password on your device to accept the invitation. You can also send them an invitation, and they can accept from their device. If you have multiple Apple IDs in iTunes, you can invite each of your accounts to the group, so you can share purchases from your other Apple IDs with your family.
After you send the invitation, you can check its status under the person's name.
- On your iPhone, iPad, or iPod touch, go to Settings > [your name] > Family Sharing. If you're using iOS 10.2 or earlier, go to Settings > iCloud > Family.
- On your Mac, go to Apple menu > System Preferences, click iCloud, and select Manage Family.
Then select that person's name to see the status of the invitation. If you need to resend the invitation, select Resend Invitation.

Accept or decline an invitation to join a family directly from your device. You'll get an invitation sent to you by email or in a text message. Then you can respond right from the invitation. If you miss the email or text invitation, no problem. You can respond from your device Settings or System Preferences:
- On your iPhone, iPad, or iPod touch, go to Settings > [your name] > Invitations. If you're using iOS 10.2 or earlier, go to Settings > iCloud > Invitations.
- On your Mac, choose Apple menu > System Preferences > iCloud > Manage Family.
To accept an invitation, follow the onscreen instructions. When you join a family, you might be asked to confirm your account information and to opt-in to any features or services your family set up.
If you can't accept the invitation, see if someone else joined a family with your Apple ID or is sharing purchased content from your Apple ID. Remember, you can only join one family at a time, and you can only switch to a different family group once per year.
Best regards.