My brother needs a wheelchair accessible ramp and shower. He has his own house. Can he get a Federal grant for this improvement? Thx

Often there are not direct grants, he can see if there are programs from groups to help with this. If he is a VET often the american Legion, or the VFW will help with those. Also there may be faith based groups in your area that help. He can also check with the local social workers to see if there are local programs they have available.
Also if he has a certain illness, there may be support groups that help.

* I am assuming this is a home he owns, if he is a renter, and it is a larger rental company, and they rent though section 8 or another government program, they may put him on a list to be moved to an apartment that has those features.

Check with your county as well. The county which neighbors mine will construct wheelchair access ramps in the homes of people in need for free or for a very low cost. Good luck to you.