This spring marked the fifth season of the NBC show, “This Is Us,” and though I have been occasionally critical of the show, including on this blog, I will miss it when it ends next year. It is not just that the show dealt with issues like foster care and adoption that I care about deeply. It is also because I am a sucker for portrayals about big, multigenerational families. Shows like “Parenthood,” “Brothers and Sisters,” and “This is Us” all portray complicated but ultimately loving adult sibling relationships, something for which so many people seem to long but fewer of us get to experience.

In our recent national conversation about falling fertility rates and who will care for our aging population, the loss of adult siblings is rarely mentioned. But the idea of being with someone as an adult who has known you for your entire existence is both daunting and comforting.

There is no doubt that sibling relationships can be fraught. As children grow apart, move further away from one another, and/or marry different kinds of people, there are often recriminations from wounds incurred or perceived as children. But there can also be a level of support that is difficult to find elsewhere. It is why these shows always appealed to me more than “Seinfeld” or “Friends,” where the characters might seem to have a lasting bond but there was nothing preventing anyone from moving away and losing touch before next week’s episode.

But over the years, I have gotten to watch siblings who have decided to settle down in the same suburb, even the same neighborhood. They seem to provide a source of support for marriages. Turning to a sibling for counsel instead of a spouse can be healthy and seem like less of a betrayal than confiding in a friend.

These adult siblings have dinners regularly and though their nuclear families are not large, the presence of cousins so often gives their children the feeling of having more brothers and sisters around. In a recent column, Frank Bruni describes the joy he derives from being an uncle. And he notes that many aunts and uncles have stepped in helping their siblings’ children in times of crisis. And they serve as a release valve for many stressed parent-child relationships. There are other trusted adults that children can complain to.

But it is not just Bruni’s relationship with his nieces and nephews that he cherishes. He writes of his sister:

I get to communicate my love for her by lavishing affection on her kids — by watching football with Gavin, who’s a Philadelphia Eagles maniac, or claiming one of the front-row seats for the production of “Mamma Mia!” in which Bella, who had a juicy supporting role, sang her heart out. That’s yet another joyful facet of being an uncle or aunt: It can deepen your bond with your siblings, adding layers to it.

Television shows like “This Is Us” inevitably contain some amount of handwringing by matriarchs and patriarchs of the family about the relationships among the adult siblings. But they also seem comforted by the idea that their children will not be alone after their parents are gone.

And the old family stories will carry them through. The multigenerational family is also the setting for many of Anne Tyler novels. In her book, The Amateur Marriage, Lindy, one of three siblings who disappeared as a teenager returns decades later. Her younger brother, George, now with kids of his own, is suddenly transported back to his childhood, shared confidences with his sister, moments buried in his past. George recalls once when his father bought a nightgown for his mother at Christmas and the parents closed the bedroom door early that evening: “At the time, the children were, oh, probably, twelve, eleven, ands seven or so—old enough to send each other embarrassed sidelong glances, although now the memory made George smile.”

In the finale of “This Is Us,” the three siblings are left with their slowly deteriorating mother to imagine what their late father would have done in a particular situation. Those shared memories of their childhood have kept them bonded all these years and will continue long past when no one else can remember their parents.