Dadamenez wrote:The children were registered on their name but got married only 3 years after the second child.
Sound like 'Children got married' You meant your friend got married 3 years after the second child.
As far as children have their dad's name mentioned on the passports, they won't face problems in visa endorsement. I trust so. What's the friend's family nationality?
Let @HRGuru review the question and confirm.