Why do the emoji always show up as question marks?

Every time my husband sends me an emoji, it just shows up as two question marks on my phone. We both have Samsung phones. He has a galaxy s6, I have a galaxy note5. Both phones have the latest upgrade. When I send him an emoji, it actually shows up properly on his phone.

We can't figure out why this is happening.

And yes, my husband is sitting in the waiting room at the Dr office watching spongebob while I'm at work 😒 lol