There are all perfect!!!!!!! And it's summer!!!!!!!!!
You and your brother do have separate accounts, right? And are you playing on separate computers, not just in different windows on the same computer? How old is the machine that you are using? Just like in your other thread, please give more details to get better help.
My laptop is ancient and I cannot possibly play two games at the same time, but if I just need to login and collect from companion tasks, it will suffice. If you and your brother are using older pc's or on an older router or other machines in the home are using your internet connection at the same time, maybe ask your parent(s) to help you troubleshoot the issue. At my house, if one of my kids was playing on the xbox and I was trying to play, both of us would experience lag. Our cable company had to replace our cable splitter because it was installed when all people did was watch television and couldn't handle the new demands we were placing on it.