He receives your texts OK? You didn't say, you only mention calls between you two.
Are you using the same apps as before the switch?
Do you both have the same carrier?
I would first text him to start a thread in your SMS app. Then once he receives it have him reply with an SMS, just a regular text, and an MMS, some kind of picture message or something that wouldn't come in as just a regular text and see which, if either, you receive.
How long has it been since the two of you texted each other prior to the switch? This might establish if the issue is yours or his.
More to that point I would check and see if he's having issues messaging anyone else by asking him to text another number in your house or a mutual friend. The reason I'm feeling like the issue may be on his end is because you've successfully received messages from "everyone" else, in your words, which I'm assuming is more than 5 or 6 people. If it were 20 or more people successfully my feeling that the issue is his would go up exponentially.
Let us know what you find and we can help from there.