Parents should avoid speaking about their siblings negatively and always remember the children are their siblings' nieces and nephews, Goldenthal says.
"If (siblings) are not getting along, it could be a really natural impulse to say, 'We're not doing anything about that relationship,' " Rosenberg says. "Kids could be stripped of those relationships and part of that is inherently unfair."
Although at one time it was unimaginable, Parham and Grubb are now training together to run a November marathon in memory of their parents. Their sons have bonded as cousins and choose to spend special occasions such as Halloween together.
"They adore each other," Grubb, 36, says.
The sisters meet with their therapist now only when they feel it is necessary.
"Jenny's married and has her son, I have my son and we have our younger sister, and that's it," Grubb says. "It's a very small family, and we understand we have a gift in each other. (It's important) to really cherish that and work as hard as we can to continue a relationship we can enjoy."
Amy Warner's experience with family counseling did not go quite as well. After trying a few sessions, family relations became so tense that she and her sister opted not to continue. They haven't spoken in months.
"I would be more than willing to try counseling again even though it ended horribly," Warner says. "I haven't gotten any sort of sign that she desires a relationship with me at this point. ... It is really important for both people to want a relationship."
Sibling relationships are often the longest-lasting bonds in life, Isay says, which adds to their importance.
"These are the people you will have known the most in your life, who sang the songs in the back of the car, who know the name of your first dog," she says. "Nobody else in your life shared those experiences."
Have you sought counseling along with a sibling to heal your relationship? What was the outcome? Share your experiences in the comments section below.