They don't look the same, they are drawn in the same style. Let's look at them in detail:
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1, 2 and 3 are all related - 1 and 2 are sisters, 1 and 3 are a mother and her daughter. 1 and 2 do indeed look like sisters - the same eye shape, the same jaw, but different eyebrows and 2's chin is slightly heavier. 1 and 3 - I'd say they are actually too different to look like relatives - different brows, different eyes, 3 has longer nose and more angular jaw. 4 and 5 are a mother and a daughter again, and this time it shows - they do look like a spitting image of each other - as they should. Now, 6 and 7 are unrelated to anyone, including each other. That's the only case where someone can say that their resemblance is unwarranted - and yet 6 got smaller eyes and fuller lips than 7, her nose is straight, her jaw is slightly softer and her nasolabial folds aren't as pronounced. (In fact, I was surprised to learn that she's about 35-40 years old, I expected her to be about 10 years younger than that.)