How can I make my foster son understand that he doesn't get as much as my real daughter?

I'm currently saving for an iPad for my daughter, and if I save expenses like getting him cheaper items from menus and such I can then put that money towards the iPad. And since she's my actual daughter, I don't see anything unreasonable with prioritizing her first. How can I make him understand this? Because he always seems to feel that he deserves as much as she does.

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I have an iPad 2 (from 2011 I think) is it ok to use?

I've been using it for about 3 years since I got it refurbished and it still works well. The only thing wrong with it is about 10 months ago I dropped it and the corn screen cracked and shattered (only about 2 inches though). It is on iOS 9 I think and is fairly fast and the battery lasts decent. It's from 2011 though so it's like 8 years old (it is not a iPad Air 2) it's the iPad after the original iPad. Is it ok to keep using I feel it's outdated and might catch fire while charging or something?
Added (1). I meant CORNER not corn lol

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