Be a dead ringer for somebody
Definition 1 of 1
Pro Tip 1/3Idiomatic Expression
Used in casual speech and writing when emphasizing a strong resemblance, not suited for formal contexts. 
You won't believe it, but Jake is a dead ringer for Elvis Presley in his college photo.
Pro Tip 2/3Not Literal
It's a figurative term; 'dead' and 'ringer' don't refer to 'deceased' or 'calling.' 
Stage actors often have to be a dead ringer for historical figures.
Pro Tip 3/3Visual Similarity
Focuses on physical appearance, not personality or other attributes. 
At the party, I met someone who was a dead ringer for my cousin. It was uncanny!