"My older brother will be in the hospital this weekend."
In English they are saying 'will be' and not using 会 huì - future tense/action
In this case, it lets you know which weekend the older brother is going to the hospital. If it's removed, it would sound like the older brother is at the hospital on any given weekend, or generally at the hospital on weekends (我的哥哥周末在医院。), so using 这个 helps the listener understand when it's happening. I hope that helps, let me know if I could explain it better!