iMessage issue when using two phones

Basically, I have two phones. Phone A(5s) and Phone B(6+). Phone A only sends and receives from it's own number. Phone B sends new messages from it's own number but also receives from Phone A which will allow me to continue conversations from Phone A on Phone B.

Sometimes I'll have an issue where Phone B will send using Phone A's number(even if it's a thread that has been ongoing on Phone B), but that isn't my main issue right now. If you have an answer on that though, please fire away.

The problem I'm having right now is that Phone A's thread is on Phone B. It is going fine as iMessages on Phone B, however iPhone A shows all the messages as Text Messages instead of iMessage. In addition, sometimes the receiving iPhone will receive pictures twice. Any clue what's going on there?