So in theory.
Gramps gets 1st daughter at 18 coming in 19.
Daughter gets pregnant at 18. Birth a son around 19.
Gramps is now 38. Decides to have another child.
Gramps is 40 now and has second daughter.
Daughter's son is 1-2 years older.
Daughters son lives with Gramps now due to circumstances. The two are raised together like siblings.
Its actually possible.
Gramps gets 1st daughter at 18 coming in 19.
Daughter gets pregnant at 18. Birth a son around 19.
Gramps is now 38. Decides to have another child.
Gramps is 40 now and has second daughter.
Daughter's son is 1-2 years older.
Daughters son lives with Gramps now due to circumstances. The two are raised together like siblings.
Its actually possible.