Thank you for your reply. It seems to me from the information you have provided that if he was applying for his wife and 2 children to enter the UK under paragraph 319 c (g) he would have fell short of the maintenance requirements. Paragraph 319 c refers to maintenance requirements.
Because he is apply for 3 applicants to join him, he would need to have funds of £630 for each applicant wishing to join him in the UK, in this case it would have been £630 x 3 which is £1890 approx in his account for a consecutive 90 days period prior to the date of application.
This would need to be in addition to him showing funds for his own maintenance of £945.00 in his account for 90 days prior to the date of application. What this means is that he would need to be able to show funds for his maintenance £945 PLUS (£630 ( for each applicant) x 3) = 2835.
In this case he would need to have shown that he had a balance of £2835 for a consecutive period of 90 days in his account prior to the date of application, if this was not the case then his application would have been refused.
It seems that he did not have the required £2835.00 in his account for 90 consecutive days and that is why his application was refused.
I hope this answers your question if however you feel that the answer does not cover all the points raised in your question please do not hesitate to ask further questions until you are satisfied with my answer.