I have a son.
It all started when we knew a beautiful woman and her daughter. After some relationships, I became my own grandfather.
Can you explain how did this happen?
It is given that the narrator (n) married the beautiful woman (w),
and so the woman's daughter(d) became his (step)daughter.
Now,n's father(f) married d, so that d also became m's (step)mother.
A son (s1) was subsequently born to n and w.
A son (s2) was also born to f and d, making s2 the (step) brother of n.
Thus, s1 and S2 are step(brothers), and n is the grandfather of s1.
Now, n is the grandfather of s2, and s2 is the step(brother) of n.
Consequently, n is his own grandfather.