Glad to hear you are making the effort to include your brother on the boat.
I have modified my Lagoon
400S2 to include my father.
Fortunately he has some mobility.
This post is not one to aid in the search for the boat but one to encourage the search because the work
you put into getting your brother out on the water
will be the best thing for you both.
We sail together every week and are creating memories that are invaluable.
We have a wheelchair ramp
that with assistance he can negotiate entry onto the boat then after a rest he slowly gets up the steps.
While inside the hand holds are numerous and he gets around albeit with some difficulty. We have to attend every move. His handrails come in very handy for everyone onboard in a nasty seaway, I added a few in my cabin
due to how well his worked.
His smile when we get my boat sailing in a breeze is priceless.