How to create child design libraries based on a master


We have a Master Design Library with all of our components, colour styles, text styles etc. and looking for a way to create Child Design Libraries for multiple brands which would be based on this Master Library if it gets updated.

It seems like I am unable to change the font family on the text styles for example from the Master text styles, is there a way to do this? As we would just need to change the font family not the size/line height.