Hi Erick,
Thanks for your excellent question. I've often vacationed at
Walt Disney World with my sister's family, so I'm happy to offer my advice. My recommendation -- unless one person is paying all the expenses of the vacation -- would be to create separate reservations for each family.
That way, each of you can easily make your own decisions about dining plans (whether to have one or which one to choose) and keep track of any expenses you charge to your room during your stay.
Even with separate reservations, it's simple and convenient to request rooms that connect or are near each other. We like to have adjoining, but not connecting, rooms for privacy. Just note your preferences when you make your reservations.
You also can coordinate your
FastPass+ reservations, your
advanced dining reservations and other plans in your
My Disney Experience accounts. You just need to link your brother's account to yours using the
My Friends & Family function.
We have found on multiple-family vacations that it is unrealistic to expect everyone to be together at all times. For instance, on one trip my sister and I took the younger children to breakfast at Cinderella's Royal Table while our husbands took the older kids to the pool. Or we've split up for golf and spa outings or separate dining reservations.
I hope that's helpful for you. Please let me or another of my Disney Parks Moms Panel friends know if we can offer other suggestions. Enjoy your family time!
Wilma