In South Africa and most countries they make use of the De Villiers numbering system.
A is always the SV/PROG. You use those two instead of A.
Then his children are b - i,e, b1 the eldest and so on.
Their children are c, then theirs d, etc.
Byvoorbeeld/eg: SV/PROG, b2,c6,d9, e1, etc.
I hope it helps.
Judi