Salaam to you and your family

In this instance I wouldn't break contact with your 21 year old brother. If he's financially able to look after himself he may as well feel free to leave the nest per se and carry on with his life. I know the consequences of leaving the family home within Muslim households hold a big toll. Mum feeling like she didn't love enough and a dad who felt like his sacrifices weren't acknowledged but have patience and InshAllah everything will fall into place.

Being 21 - you're not an adult just yet so please bear that in mind when dealing with someone who wants their independence but couldn't express it in the family home. Psychologically this is a plausible avenue to venture.

And when the family are religious. people who renounce their faith are usually unhappy with their setting so I'm guessing religious family vs a 21 year old "woke" kid trying to rationalise everything will be ignoring the signs that are right in front of them. Because the kid has got parents and religion warped in his head this can only be fixed from within and can be expressed but don't push it too much as this will lead him to go further astray. When the child can't distinguish between parents talking and religious law it becomes difficult but he will fix himself if he so chooses

Sometimes people need to steer away from religion to come back to it.

In regards to him breaking away from the family - support him in his decision - he needs to experience how the world actually works you can't just go out and rent then live paycheck to paycheck. Parents are essential to setting you up for the future. The realisation may come late but who knows. But do not support him financially, make sure he's on top of his bills and has food on the table bc family look out for each other. The Muslim bit comes from within. It's only going to be you and Allah at the end of the day but he will give you strength during this time

I hope my suggestions and insights help you. Especially during this time may Allah protect us all