As a young boy, Leonard Testarossa had walked in on Maria sleeping with a man who was not his father while Carl Testarossa was abroad. When their house was stormed, Maria was able to hide Teletha Testarossa away, but thrust Leonard to the enemy. The children’s genius was well known at this point, and she likely hoped that giving him to them would get them to spare her, and Tessa. It’s likely she did this so willingly in an attempt to preserve her lifestyle, simply because Leonard knew her secret. They killed her anyways, and the two kids would have been kidnapped if Borda had not arrived after being contacted by Carl and saved them.