Thanks for your question. It's not good news unfortunately.
He would have to apply for a dependent's visa to remain here permanently. The follow is part of the eligibility criteria for such a visa:-
- He is completely or mainly financially dependent on his children or grandchildren
- He has no close relatives in his own Country to help him
Being economically dependent can mean, for example, that he has £200 to live on each month and you contribute £50.00 per month to reach that income. If he is financially independent then the application will be refused on this ground.
Similarly, if your sister is in Pakistan and available to help him then it would also be refused on this ground.
On the above two issues it would be unwise to submit an application for a dependent's visa.
I'm afraid you will have to put up with him periodically applying for a 6 months visitor's visa to come and see you.
Sorry it could not be better news.
If this has been useful please kindly click accept so that I may be rewarded for my time. It will be gratefully received and you will be free to ask follow up questions.