Video player creation in python
I'm not sure on the synchronous video side, but this related post may help understand more about potential limitation regarding video in tkinter
Way to play video files in Tkinter?
Hope this a helpful...gl
Qt lets you play videos using the QVideoWidget and QMediaPlayer. There's an example player for PyQt.
For Tkinter there is no default widget for playing videos. You can play videos with tkinter, but this is not using one of the tkinter widgets and a bit hackish. See this answer on stackoverflow
Synchronizing is tricky with videos, but possible. You would have to set the videos to start at the exact same time, with the same frame rate.