Your bro has A Sun Pluto opposition across the Asc Desc with Sun Mercury & North Node in the 12th (as you probably know)
There may be a familial thing & a personal thing for your brother re his autism - like he may have chosen this option this time around to go within in his life time
I have a feeling tho that later in life he may work his way thru the autism.
He has a very rich inner life & could have a very rich artistic interest too.
With the your mercury's conjunct I am sure he IS connecting to you very much.