If you are a child over 21 years old, or a relative (parent, Brother Sister, Grandchild) of an EEA national and depend on them,you could apply for a Family Permit Visa, in order to guarantee entry to the UK in this category.
You need to show that you are dependant on the EEA citizen and they are in the UK/or coming to UK in order to work, study or live in UK as self sufficient in exercising their free movement rights.
If you apply for a Family Permit, you need to show that you are financially or emotionally dependant on the EEA national and that the EEA National is a qualified person in UK.
You would be granted 6 months entry clearance and you can apply for a Residence Card upon arriving to the UK.