We know little about Erwins past, but from what we have seen, we can say for sure, that he shared a tight bond with his father. Erwins father was a teacher and a very intelligent man, who I assume was a man with a very kind heart (he teaches children >>) and refined manners. He passes this down to his son, whom he educates at school as well. When he found out that Erwin shares the same interest in the world he does, he let's him in into the secrets he discovered and shares his dream. Being a child Erwin was excited about the new world, about the secret that was forbidden to get out, but he had to tell someone, just like Armin told Eren.
But he trusted the wrong person with it and his father had an "accident". We all know that he was killed by the MP to give Erwin a warning and to stop a teacher from teaching the wrong views. Erwin didn't proceeded this well. We can only assume who raised him from that point onwards or how his life had been, but what we know is that he blamed himself for the death of his father and with that in his heart he made his father's dream his own and he worked hard to make the dream come true. He ended up in leading the survey corps with his vision and his ambition, that was passed down by his father.
Erwins grieve about his father's death was so deep, that he was never able to fully get over it. He mastered the ability to push any thought about him away. It changed his life. Knowing how much it hurts to lose someone because of you, he didn't refused to love, but he refused to engage in it. He cared for the people, that stood close to him like Mike, Hanji, Nanaba and Levi even commander Pixis and Darius, who proved to him to be loyal friends. He had encountered betrayal by Nile not following him, despite saying so and by taking the woman he had loved, but Erwin was clever enough to see that Nile was a good person, treating her the right way and that eased his mind and heart. He may seem like a heartless devil, sacrifice lives, but his past formed him and he had a secret way to care for the people around him while still following his father's dream.