There's individual PassPlus, which allows spend for PassPluss member and up to 8 on same record. You'd have to figure out the amount of spend you and family members would get to traveling together. As I understand it, you have to fly every segment booked (with or without others). You can't book and then cancel out to let the other fly. The sum of the PNRs with your name on them as a passenger would need to get to $75k. You put the $75k into a PassPlus account at Chase/United prior to getting GS and being able to book. You then get a UATP account that you draw down through the contract period.

United's not going to give you GS for being a travel agent for other family members. They're smarter than that.