Merge or move members from one family to another

Hi, me and my girlfriend are going te live together. We both have kids. I have a family set up with my kids and share Apple Music, icloud+ and AppeTV+.

I would like to add my girlfriend and her 2 kids to share my Apple Music, icloud+ an AppleTV with them.

My girlfriend already has also setup her own familiy sharing with her 2 kids including Apple Music and icloud+. So she has to remove her familiy members and stop her Applemusic and icloud+ services…offcourse we would not like to pay twice in the same family ;-)

She can offcourse remove her kids as members and stop the services…

But….

They really would not like to lose their data, like playlists in AppleMusic and documents and photo library from icloud+.

How to make this happen??