Naturally curly hair is pretty common as it's estimated that between 55 to 65 percent of the world population has naturally curly hair.
Some people are born with the type of hair that causes naturally curly hair and then later on when they get past the toddler years the curly hair can change from curly to straight.
However some peoples hair may stay curly the entire life of the person.
If someone in your family has curly hair or the mother or father has curly hair then your baby may be born with the trait of curly hair.
I like curly hair on toddlers as it looks very cute but my nephew didn't think it was cute as he hated when I would say how cute his curly hair was when he was little.
It now has changed to straight which he likes more and he's almost 18 years old now.