Thank you for your question
My name is ***** ***** I shall do my best to help you.
There is no basis on which your brother will be able to obtain any form of Guardianship for the child UNLESS for some reason it can be proved that the child is at risk of significant harm in her care.
Even if that was proved you would actually be expected to return to the Uk to take on the child
Having said that the law says that a child is entitled to contact with both sides of her family and the courts will enforce this if necessary
You can apply to the court for a Child Arrangement Order setting out times for Skype and Direct Contact with you - and for once a month contact with your family while you are away.
With regard to finances the way forward is simple.
If you do not send her money then she will have to aeke her own arrangements.
For now pay the mortgage plus 12% of your gross income as Child maintenance - the rest is up to her
Please ask if you need further details