It's not a bug. They added this feature in the sims 3 PC game with into the future EP and carried it into the sims 4. This mobile game is a dumbed down app version of the sims 4 for PC. It's a game not real life. Some people with same sex sims wanted the feature to have genetic children from their two sims rather than only being able to adopt. When you use the genetics in this game , the children look like both parents.
