Hi,
I know that in Spain
child maintenance is not dealt with the same as in the UK. Whereas we tend to use the CSA more often than not, in Spain you have to use the court system.
There is no set percentage to be paid like the CSA, your friend will have to ask for whatever she thinks is reasonable to cover the cost of living, housing, education, clothing and medical provision. If both parties are in agreement to the amount asked for, then great. If not, the courts will look at the NRP income and expenditure. Also,
child maintenance does not necessarily stop when the children reach the age of 18.
I have friends who live in Spain, and typically, for 2 children, approx 30% of the NRP salary would be awarded.
I hope this helps. I am sorry but cannot advise on custody/contact, but hopegully someone else on here may know.