COUPLES BREAKING THE 'KISSING COUSINS' TABOO... JOHN STOSSEL REPORTS ON ABC'S "20/20," AUGUST 6

Plus: Victoria Gotti Talks to Deborah Roberts; Bob Brown Profiles Comedienne Joan Rivers; A Full Circle Adoption - JuJu Chang Reports

Kissing cousins...Is marrying your cousin more than just a social taboo? Many people assume that married cousins will have kids with birth defects. But a recent groundbreaking study funded by the National Society of Genetic Counselors revealed the assumptions about cousin marriage may be unfounded. The head of the study, Robin Bennett, says: "We didn't say there wasn't a risk; we were saying that the risks are not as bad as people perceive." In fact, the parents of one of history's smartest men, Albert Einstein, were cousins and he, too, married a cousin. John Stossel's eye-opening report airs on "20/20," FRIDAY, AUGUST 6 (10:00-11:00 p.m., ET), on the ABC Television Network.

Every year about 200,000 cousins marry each other in the United States. Worldwide it's even more common - 20 percent of all married couples are cousins, and in some Middle Eastern countries almost half of all marriages involve cousins. So who are these couples? "20/20" talks to two married cousin couples -- Mark and Christie from Nevada and Brian and Caren from Michigan -- to find out why they fell for each other and how their families and friends reacted.

And: The latest reality show star, Victoria Gotti, speaks candidly to Deborah Roberts about her hot new television show, "Growing Up Gotti," raising her three sons as a single mom and being John Gotti's daughter.

Plus: Bob Brown profile famous comedienne Joan Rivers, who has gone from a solo stand-up comedy career to a mother-daughter act on the red carpet.

And: What if your grandmother were also your mother or your sister were also your child? JuJu Chang reports on a family with extraordinary ties from adoption.

ABCNEWS.com, the 24-hour news service of ABC News and part of the ABC Internet Group, will provide companion programming to the broadcast.

"20/20" is anchored by Barbara Walters and John Stossel. David Sloan is the executive producer.