I posted a photo of myself with my sons on Mother's Day and had loads of comments from family and friends about how they don't look at all related. I have actually had a random in a shop ask if they have different dads.
DS1 is slender with blonde hair, green eyes, a dimpled chin, and definitely features from my Dad's side of the family.
DS2 is rounder with dark brown hair, blue eyes, a button nose, and looks exactly like DH.
Do your children have a family resemblance, or are they like mine where you would never guess they're brothers?