My son is the sweetest kid I know (don't tell my daughter I said that). He is kind, compassionate, and constantly happy. Last week, while he and his sister were playing on the living room rug, he threw a toy and accidentally hit her in the face. She started to cry. At first, he sat in what looked like slight terror, but then quickly walked over to her, hugged her, and said he was sorry. No one prompted him, either. He did so all on his own. He displayed compassion, and while raising compassionate sons isn't very difficult, there are definitely thing parents do that can hinder the process.
I can tell my son is very in-tune with his emotions. He is constantly observing people's reactions, and he is very affectionate. He randomly tells his fathers and I that he loves us, all day, every day. He comforts his friends and his sister when they are upset, and he reminds us that the cat is hungry when she starts to meow. He is sensitive and empathetic and caring. I do believe that in so many ways he was born this way, and both of his parents and their families are empathetic people. But compassion and empathy aren't just innate; they require fostering and promotion.
My husband and I went into this parenting thing without any experience, obviously. We weren't given a manual, and still, to this day, we are mostly just winging it and using common sense and logic to the best of our ability. The one thing we learned early on, however, is that children need parents who will listen to them and who will validate their feelings. We do our best, every day, to show and model empathy and compassion. So, if you want to raise compassionate boys, here are some things you may want to avoid: