Yes I'm sorry for that but he will be safer and the children will be Spanish and can decide for themslves anyway.
We were told by the British Consolate that DD1(born in the UK) that dual is not possible, although she has a German father, as she has to be 18 to make this decision for herself.
It is easier now but when she went to Berlin with the school before the wall came down, she had to get out of the coach and walk through Check Point Charlie on her own. She finally became German a few years ago and now has both.
Mamie we never wanted Brexit, we know how valuable Europe is
especially in this insecure world.