This is from Emirates' own Skywards program:
Family Bonus** 20% of the miles flown are added to the family head's account*
** A member can nominate up to eight family members for the Family Bonus programme. However, Family Bonus members do not earn Miles themselves.
I've done this in the past when I flew Emirates a lot, with miles from my wife and in-laws getting credited to my account (only 20% of what they would've earned themselves).
Not sure if they let you do that if crediting to a UA mileage plus number.