macky
I can see the need for making application quickly.

The outcome of any sole responsibility application will depend heavily on its own particular facts and circumstances, and the ability of the sponsoring parent to provide evidence.
This is quite a complex application and I would strongly suggest good quality and experienced legal representation.

I am certainly not suggesting you should not try. But have you considered if your son might stand a better chance by applying as an adult under his own application ??

Here are some ideas to consider when preparing your evidence for sole responsibility:-

The period for which the parent in the UK has been separated from the child

What the arrangements were for the care of the child before the parent migrated to the UK

Who has been entrusted with day to day care and control of the child since the sponsoring parent migrated

Who provides, and in what proportion, the financial support for the child’s care and upbringing

Who takes the important decisions concerning the child’s upbringing, such as where and with whom the child lives, the choice of school, religious practice, etc

The degree of contact that has been maintained between the child and the parent claiming ‘sole responsibility’

What part in the child’s care and upbringing is played by the parent not in the UK and that also the parent’s relatives.