피는 못 속여 (Pee Neun Mout Sok Yeu)

피는 못 속여 (Pee Neun Mout Sok Yeu)
피는 못 속인다 (Pee Neun Mout Sok in Da)
피는 못 속인다고 하더니 (Pee Neun Mout Sok in Da Go ha du nee)
means,  
If someone acts like his parents or ancestors 
It is used to look exactly like the person's parents or grandmother.
Also, when they look the same outwardly, they are short or tall, they have bad eyes or good eyes. or eye color, It is used in many areas, such as similar speech. 
It is used positively and negatively also.

피는 못 속여 (Pee Neun Mout Sok Yeu)

For example, 
One of the parents was an athlete, and the children were good at sports.
or 
When your parents were scammers, and your children were lying,
in a similar phrase..
The apple doesn't fall far from the three.