... it lists both their names or survivor to them.
Does it perhaps actually say "... to the survivor
of them?"
If you want a definitive answer, arrange a consultation with a probate attorney who can read the entire document.
If you'll settle for semi-informed speculation, my guess is that the clause makes a bequest to both of your parents or, if one of your parents passes away before the friend, to your surviving parent. Unless there is some language covering the possibility of both of your parents predeceasing the friend, then the bequest would lapse and become part of the residuary of the probate estate.