Because I was sure I was going to kill him, at least when he was younger.
Let me explain a bit. He's my stepson, the product of my wife and her deceased first husband. When I met my wife and her (now our) daughter and son, they were about a year into getting over the loss of her husband and their father. I never knew this man, but from what I've always heard from my wife, the kids and others, he was a fine man with no obvious character flaws. He was quiet, considerate, exceptionally intelligent and skilled in his work (he was an engineer). In other words, he and I could not have been less alike.
Anyway, when I met my wife and the kids nearly twenty-five years ago, our son was eight, our daughter eleven. As I tell people, I married a family, complete with a dog and a station wagon. We all got along well and developed good family relations. I helped our daughter with her homework (particularly English papers, which she hated) and helped our son, too, but he didn't act as though he needed all that much help.
As he got older the same thing that so typically happens between fathers (even stepfathers) and sons happened to us: he decided he knew best for himself, and essentially stopped listening. Not just to me, but to anyone outside of his immediate circle of friends. And he got into a bit of trouble. And that's when I was most ready to kill him.
Of course, I didn't. He went off to college, lived with us for some of that time, but with roommates most of the time. He even went off to West Virginia the summer after his graduation, ostensibly to be a rafting guide on the New River (good work if you can get it), living in a tent (!) with others in the same line of work. Then he decided to move to Colorado (where our daughter and her husband already lived), as he had a friend at a ski resort who promised employment.
All through this I questioned his logic, but make no effort to prevent him from carrying out any of his plans. "It's his life," I told my wife. "He has to do this for himself." At certain points when he was in Colorado, far away from his support system (except for his sister, who looked in on him every couple of weeks), my wife even suggested we send him money (he had some very bad luck in working on a construction job that failed to pay him regularly and then he discovered they had not paid into the unemployment system on his behalf), but, again, I suggested that we not do that, as he needed to shoulder this responsibility for himself.
Well, he called on Saturday about seven years ago and asked if he could come home and live with us. "Of course," I assured him. Plans were made and he arrived back at our house, with his dog and what few belongings he elected to bring home with his clothes. I had him sign a set of "house rules" to assure that his living with us wouldn't be disruptive; he agreed without complaint, despite my wife's enormous objections!
He was home for a few days and I reminded him that he would need to get a job ASAP, so he did. He then reconnected with the young woman to whom he's now been married for about five years, learned of a job within the local court system, and he's developed a decent career path since that time.
Most importantly for me, though, is that not only did I not kill him, but we both subconsciously agreed that we had missed each other, and began spending time together. Much of our time revolved around baseball, but that was an early common interest for the two of us starting when he was a kid and I was appalled to learn that he knew nothing about baseball.
He's written me a lot of birthday and Father's Day cards over the years since which indicate without question that he appreciates me as much as his mother, and the relationship we've forged. He's probably my best friend, except for my wife.
Happy birthday, son. I love you!