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.