EEA Family Permit - Can child Sponsor mother and sister?

Hello all,

I sincerely value all helpful replies to this complex query, it is a very stressful scenario without legal help and I am hoping someone here may know a few possible answers. I am hoping an EEA Family Permit may be at least part of a solution to our immigration situation, though it may not be a complete answer for all family members involved.

I am a British Citizen in a de facto relationship with my partner currently both resident in Ecuador, we have been here for just over two years. We have a baby son, now 7 months old, he is entitled to British, Australian and Ecuadorian passports. My partner has two daughters from previous relationships, both currently reside fully in her care and fathers have had rights removed legally.

My partner is an Australian/Ecuadorian with a Spanish Resident Card until 2016 but has been out of the country for longer than the allowed period it specifies. She is currently still married to her former Spanish husband but is in a divorce process here in Ecuador.

The eldest daughter is 13 and holds Australian/Ecuadorian nationality and has a Spanish Resident Card on the same terms as her mother.

The younger daughter is 10 and holds Spanish/Australian/Ecuadorian nationality and her Spanish EEA passport is current.

We would all like to move to England and settle permanently near to my relatives there. It would be most likely that I would go first alone to get a job and find a house, initially living with my parents to save money faster. I would want my family to follow as soon as possible. I have no notable income from the previous 12 months and would be reliant on financial support info based on the new job, if such be required.

My questions is whether there is a way for the younger daughter to come to the UK on her Spanish passport and bring her mother and sister by means of a EEA Family Permit? If a reason is required for her to come could it be that she is dependant on me or simply coming to start school here, or some other valid reason? She would join me at my home and I would be responsible for her wellbeing. I expect the answer to be no on her sister, but is it a yes on her mother? What grounds do I apply for the Permit on?

Assuming this route is feasible could we then somehow sponsor the elder daughter to come with them by means of another visa and if so which visas would be best?

I have some experience of UK Visas having previously been married to a Thai citizen (since divorced) and managing to get her visas and then later to get visas for her daughter visa complex case with several appeals involved. Yet in this instance I am befuddled by the complexity of this potential multi visa requirement for my family.

I am considering using a lawyer to get advice but some initial guidance would be very helpful.

Many thanks to all.