If 'K $\times$ L' means K is the father of L, 'K + L' means K is the wife of L and 'K $÷$ L' means K is the brother of L, then what is the relation of N with P in 'M + N $÷$ O $\times$ P'?

Let's dissect the relationship string structural model of 'M + N $÷$ O $\times$ P' expression path components:
* $\text{M}+\text{N}⟹\text{M}$ is the wife of $\text{N}$ (meaning $\text{N}$ is a male).
* $\text{N}÷\text{O}⟹\text{N}$ is the brother of $\text{O}$.
* $\text{O}\times \text{P}⟹\text{O}$ is the father of $\text{P}$.

Since $\text{O}$ is the father of $\text{P}$, and $\text{N}$ is the brother of $\text{O}$, $\text{N}$ is the paternal uncle of $\text{P}$.