Yep, he does. If he never had me (specifically a sister) in his life, he wouldn’t have become the person he is today. I made him a nicer person. I apparently warded off his “feelings of loneliness, guilt and fear” as well as boosting his confidence. I also encourage in him “a spirit of generosity” and reduced his risk of depression. This is all “official” following the study done by researchers at Brigham Young University.
Of course I also (and the study doesn’t mention this) developed in him patience (when I badgered him for attention or to help me with something), a spirit of forgiveness (when I traded his favourite toy car, for one that I preferred!), and a sense of responsibility (my parents expected him to “look out for” me).
Gee, he sure has a lot to be grateful for! ;-)