iPad messages not being marked read after viewing them on iPhone

When I pull up my iPhone and check my unread texts through the messages app and then I open up my iPad, it will say I have 20 unread texts. All are a mix of SMS and iMessage. Some iMessage texts will be marked read, but other iMessage threads will still show as unread. Same with SMS texts.

No amount of waiting for it to sync marks them read.

When I check my texts on my iPhone, I would expect that the iPad messages app would mark those same text messages as read and this is not the case. Is there a setting I can change to get my iPad and iPhone to mark text messages read when I check them on one of those devices? I'm basically having to check half of all my texts twice.