If he entered over the border without inspection then he will need to adjust through 245(i) as you say. You can file for adjustment of status (form I-485) now and show evidence of the approved I-130 that you filed and the I-130 filed by his brother for 245(i). I understand that you cannot afford an attorney but in my opinion you will need one for such a case. Look around for attorneys that may offer you a payment plan.
I agree with Ms. Maylov. These types of cases are best handled by professionals. In particular, when 245(i) is involved.
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Hello hope you are well. If he entered the US illegally then the 245i is essential in his case if he is going to adjust. If the I130 was approved file that along with the I485 and the supplement (245i) with USCIS ASAP. If you have any doubts you should contact an immigration attorney or go to catholic charities and seek out some guidance. Best of luck to you!
You should definitely hire an attorney. You can go to a private attorney or see if a non-profit can take your case. I volunteer at one in Oakland called the International Institute of the Bay Area. Good luck!