Third: sexual development. Yes, children already develop their sexuality. Young toddlers who are toilet training like to talk about this. Children between 3 and 5 years like to touch and play with their genital organs. So when you see your kid do this, it is very normal at this age. From the age of 5 to 7, children have a crush on their parent of the other sex. It is very normal that they talk about wanting to marry the parent. This will cause a love-hate relationship with the parent of the same sex because they see them as a competitor.