Blue Yeti Microphones for Podcasting - weird feedback

Hi - I am working in GarageBand on creating a podcast. I am using two Blue Yeti microphones connected to my 2017 MacBook Pro. Normally, I can monitor my own sound through the microphone itself and some headphones. At one point, I was also able to monitor the other speakers audio through my headphones. Is there a way where both microphones will be able to monitor the audio from both microphones? I've created an aggregate device, connected both microphones, and can record two separate audio tracks in GarageBand. But, if I select the option to monitor on both, there's a weird echo and it sounds awful. I can select only one to monitor, but one person would monitor both, while the second person can only monitor themselves. Please advise.