My eldest (half) sister and I look so alike that, when I reunited with my dad's side of the family about ten years ago, her boyfriend asked me if I was her sister and I don't think he even knew she had another sister! Our colouring and features aren't quite the same, but our expressions and the set of our features are so alike it's almost uncanny. Our middle sister looks a bit different but there's still some family resemblance.
My younger half-brother, who has the same mom as me, doesn't look like me at first glance, but we have the same shape eyes although his are blue and mine are green.