In a way, it's beautiful that your brother doesn't want to be part of Faith and Light. He's saying: "I'm not a handicapped person." Today we encourage people to develop their abilities and, when possible, to hide their differences.
That's good in one sense. But there's another side to it.
I suspect your brother struggles to fit into society, to find work that suits him, to live outside the family.
There are places where he might find his place—integrated theater groups, a hiking club, a parish choir. But the real question, don't you think, is this: have you sat down to talk with him about what it means to have Down syndrome, to have trisomy 21, and what that entails? Not so he simply endures his handicap with anger and sadness, but so he might accept it, even welcome it, with love. So he can see past the handicap to the person underneath—his true, intimate self, his heart capable of loving.
To love who you are: "I am what I am, with my weaknesses and strengths, with what is unique and different in me."
This remarkable acceptance of oneself and others begins in the family, in the neighborhood, in the parish, at school—and then throughout life.
Learning to accept being different, with your own limits and fragility, takes time and needs good support. Who could help you walk your brother through this?
In L'Arche as in Faith and Light, the gap between a disabled person and the assistants or friends can be visible—sometimes too sharply drawn. There are pluses and minuses: you can either retreat into your handicap or you can deny it.
Society itself is complicated. How can your brother accept himself as different when so many others won't?
My hope is that he finds a circle of friends where he can be happy and proud to be who he is: a child of God and a human being more beautiful than he believes.
That takes honest words that don't shy away from suffering—something all of us face—so he can move from an idealized, imagined life to embracing reality with all its beauty and sorrow.
For all of us, peace of heart grows in this embrace of what is real, in how we learn to live actively, joyfully, and wisely.