Ok ... let me see. You have a single member LLC which files a Sch C ... if so it cannot own 20% of anything since it is a disregarded entity. The K-1 that you receive (even if it is in the Sole prop EIN) is entered in the Personal income section as a K-1.
You do NOT want it to be entered on the Sch C where you will have to pay SE taxes on it.
Now the Sole Prop could preform work for the other LLC and get a 1099-NEC for the work ... that would go on the Sch C.
