Maybe there are pairs of states that could work for your kids, with the engineer in the light blue state and the LAC(? I assume) student in the dark teal state? Like engineer at Marquette in light blue Wisconsin (although Milwaukee and Madison are the liberal areas) and the other in the dark teal Illinois? Same with PA and the surrounding states that are teal.
Even in the dark teal states, there are going to be areas of the state that aren’t friendly to all and any college can be in that area. The same with liberal areas of ‘not friendly’ states, but the trans kid probably wouldn’t want to live in even a friendly city of a not friendly state (but might be okay to visit).
But the second student wouldn’t be living in the light blue state just visiting. Same could be true of schools near light blue PA (Maryland, NY) if the engineer likes schools in Philly. The OP is looking at small rural schools in upstate NY which may not be as accepting as bigger cities if living there, but visiting may not even be an issue.
It’s not quite as simple as literally expecting his brother to visit. That might happen, and if so he would absolutely want his brother to feel safe and welcome, and not feel anxious about the travel or the environment.
But unless they are quite close, my guess is that rather than visiting each other often they will make sure to be home at the same time, in bright blue Maryland.
The reality is that being his brother’s twin and protector and advocate is a large part of who he is, and being in a place where that piece of him is safe and acknowledged and celebrated is important to him. Plus I think he would feel disloyal to use his privilege to go somewhere his brother couldn’t go? I am not sure I am explaining it well.
He does have some schools on his list in PA (Pitt, Temple, Drexel) and VA (VCU) which satisfy his desire to stay close to home, and of course they are young and have more than a year to go before applying. So, all this might change.