Estrangment from family member excercising treaty rights

My client is a 17 year old Dutch National who entered the UK as a 12 yo with his parents.  His father who is also a Dutch national was working here at the time when my client enetered education.  He (the client) has been in education ever since and has now just statred his A level year.  The problem is he is now estranged from his parents and has been refused IS because DWP say he does not have the right to reside - I think he does have the right to reside as he enetered education while his father was working here.

My questions are - does his estrangement from his father affect his right to reside?
Due to the estrangement he will be unable to provide any written proof that his father was working at the time he entered education, any suggestions as to how to deal with this? 

Cheers folks

As well as the Art 12 right mentioned by Dan, your client is still a family member under the EEA Immigration Regs 2006, simply by being under 21 - estrangement does not affect this at all. The issue   for this is purely if his dad was a worker or had retained worker status at the time of his claim for IS, which may be straightforward.

Thanks folks, I did eventualy manage to find the bit about not needing to be dependant after I posted my query, just couldn’t see it for looking before.  Its always nice to check though, no point looking silly at a tribunal any more frequently than is strictly necessary, even if it does provide free entertainment for the judiciary!  :-)

Your help is appreciated, as always.