You can add children to your application as dependants if both of the following apply:
they are under 18 when you apply, or were under 18 when they were first granted leave
they do not live an independent life
Your child is living an independent life if, for example, they’ve left home, got married and had children.
If your child is from your previous relationship, you must prove that you have had the sole responsibility for the upbringing of your child for your child's application to be successful.