Each league will have their own division and round-robin with their own schedule.
But you can create a Stat Group with both of them together.
First step, Go to Manage, Statistics/Standings, Stats/Standing Grouping.
1. Choose the Player Page.
2. Click on the Plus.
3. Name your group (ex. Sunday/Tuesday 8 ball)
4. Select the two groups you want to pull stats from under Bracket/Charts.
5. Choose a Model of Statistics if you need a specific template.
6. Save.
Then go to Manage, Brackets/Round-Robin, Round-Robin, Select the two leagues. (Hold Ctrl, with your mouse click on each league while still holding Ctrl)
1. Click Pencil.
2. Go to Advanced Section
3. Set your Default Stat (Player) with the Merged stat group you created.
4. Save.