I remember my childhood sweetheart, she was actually my first love! Did you have a childhood sweetheart?
We do ,could remember mine too
They say usually a childhood sweetheart is a platonic relationship and generally doesn't last very long.
Well ,don't you think there may be chanced that out of 10 ,1 could last?
Perhaps, but sometimes even after an initial relationship ends. These friendships are rekindled later in life and sometimes lead to a later life marriage or partnership
So what other types of relationship exist?
There are many such as coutrship, close friendships, engagement, marriage, acquaintance, etc. The childhood sweetheart relationship often forms the basis of relationships later in life! 
OK, so what do you regard as courtships?
A courtship is the period of a relationship before engagement. So basically dating!
How is it different from a close relationship ?