Incoming Facetime call from my husband's ipad

When I Facetime my husband, it rings on his iPad and iPhone. When he Facetimes me from his iPad, it does not ring on my end, but when he Facetimes me from his iPhone, it rings on my end. I have looked at all my settings, and I cannot figure out why this is. Any ideas? Also, when I want to Facetime him, I have to go to his contact and Facetime him from there. I cannot choose the Facetime app on my phone.