Castell in South Africa

[the red swift]

My grandmothers brothers George Castell (b 21/10/1878 Kingston upon Hull) and Alexander Castell (b c1890 Poplar, London. d1956 SA), both migrated to South Africa.  I have been unable to trace any information about them except that Alexander married a Kathleen Florence Heath (d 1966 SA).
I would love to know if anyone has any information about these two brothers.