Have you tried to verify the files via Steam? That sometimes works like a charm. Same with repairing the EA app. And are you using the same Steam account for both your siblings or do they have their own? In case it's the latter, you could try and make it available via a family account. You can do that via settings - click on "Steam" in the top-left corner, then choose "settings". There's an option to create a family library which will allow you to share games with others. I don't know all the steps, but if you go to Steam's support page and search for family library, you'll get a detailed description that guides you through the whole process. Not sure that's gonna work, but maybe it's worth a shot :)