Step-siblings, who are often less close than half-siblings or full siblings, often deal smoothly with parental breakups, experts say.
"The step-siblings I've talked to--and I've talked to lots--usually get along pretty well with each other and usually they would want to maintain some kind of relationship unless there is a huge age gap," said Marilyn Coleman, stepfamily researcher and co-author with husband Lawrence Ganong of "Remarried Family Relationships."
Robert's mother and stepfather were married eight years. During that time Robert, his older brother and his older stepbrother became close. Although the three spent time in different boarding schools, Robert looked forward to vacations spent traveling, skiing and duck hunting.
"I very much looked up to (my stepbrother). He taught me to ski. He taught me how to shoot. He taught me how to do a lot," said Robert, 31, of Los Angeles.
Robert said he and his former stepbrother, now 35, have remained as close as brothers for the 15 years since the divorce.