You can't convert someone into your faith, even siblings
A baby can die by mistake
Now pain, is it really pain, ex.Shaheeds, but do they feel it, or what?, pain is NOT KARMA, pain is a really confusing topic, what is the idea of pain, if one gets pain, does it affect them
Even if he is an Atheist, I think he should still keep his Kesh, only for the reason that he can prove that he is not a Sikh for the Kesh problem