Well I think that the op should seriously consider doing several things.
- Report to the local social services.
- Additional report to the safeguarding team as it may be a separate department.
- Report to the NSPCC.
- If you know the school, have a chat with the head about all the concerns.
Do not assume that each of the above will inform the others, as they may not be allowed too, or they may not bother contacting the others.
Once you have done all of the above and given them lots of detail, wait a few weeks and then recontact them once again, to check if they are acting on your concerns.
Do not just assume that all the department's will rush to sort this quickly, as there are often reports to be written, interviews to be done with both parents and possibly at least one or both of the children may be interviewed to see how they see their day to day living.
Add to that it might take time for these departments to respond, as they may all have high workloads and other just as difficult cases to deal with, within the area.
Just because the op has witnessed certain things that look like neglect to most people, it could be a sad way of life that has gone on for all of the children's lives and they do not see anything different.
Having written the above, the older one may well be starting to resent the home life, when they compare it to what they see each day at school and those kinds of hidden feelings, could potentially cause long term issues, on a emotional level.
I would also be very concerned about the girls families as clearly the Father and possibly other family members are either doing nothing to help, are not interested, or have been told to not interfere in their upbringing.
A further idea might be to see if either child is involved in any youth groups and if they are, to chat with the leader, as within some groups there may be a group social worker person, who can do something to help or advise the ok about the best person to contact.
I hope that the op can feel able to report all the concerns that they have and see real action taken to give the girls a better life.