I hope my question is as straight forward as it seems to me, but I'm trying to accurately represent an existing duct system that has a conversion from 1 duct into 2 smaller ducts that run parallel to each other. In the linked picture, the top is actual duct and the sizes that I intend to use, below is just detail lines showing how I would like the connection to display.
The Rectangular Transition Pants - DTL family that's included in your base revit families will get you about 60% there, but it lacks the ability to put a spacer between the openings as well as ability for the split to be something over than a 50-50 ratio.
It does have pretty good parameter control on the splits, and the connectors do function properly for airflow calculations, so this is probably a good starting point. You'll just have to work on the entry split parameter control.
