I have an exchange student from germany I'd like to give temporary access to my phone plan

Recently my family and I have accepted a German college student into our house a a few months. As you know roaming fees outside of your provider's country is quite expensive. I was hoping there was a way to temporarily add him to my plan so he can use cell data without blowing a bunch of money unnesesarily. Is there a way do this or would I have to purchase an entire new sim card and phone line?

Any help would be greatly appreciated. Thank you.

-Dylan