For your Bio 101 lesson of the day, I want to explain genetics.
The child's adorable little dimple is NOT from you Great Aunt Olga. You cannot attribute the brown hair to the child's mother's brother. Well, you could, but then you'd be wrong.
DNA comes from the parents. Dad's brother had nothing to do with the creation of this child (well, at least we all hope). So no, that little girl did NOT get her straight hair from Uncle Isaac (unless there's something we don't know). She and Uncle Isaac may very well have inherited the gene that determines hair type from the same source, though, but there is no possible way he passed it along to her SINCE HE PLAYED NO PART IN HER CONCEPTION.
Now that I have shared this information with the world, there will be no reason I will have to refrain from smacking someone the next time one of my father-in-law's sisters says something like, "Oh, she gets that dimple from her great aunt." Knowing, after all, is half the battle (the other half is BEATING SENSE INTO PEOPLE).
While we're on the topic of biology, let Professor Reiza tell you that, in the case of twins, the mother is the only one who determines that. Don't go patting dad on the back for doing anything spectacular. It was mom who either released two eggs or provided conditions in which a single egg could split. Also, you can save yourself the trouble of inquiring as to whether or not twins run in the dad's family. See above. Although, a father can pass down that genetic tendency to his daughters if his mother had fraternal twins. However, if his father's mother had twins, then nope, no deal.
My favorite response to, "Do twins run in your family," is, "Now they do."
Professor Reiza would also like to remind you that, when the answer to, "How far apart are they," is "One minute," chances are that they're twins. Please don't stare at the parents with your brow furrowed completely unable to comprehend that any children could possibly be a minute apart. Please don't follow that question up with, "Are they sisters/brothers/cousins/guinea pigs?" And in the case of flustered parents of twins of any age (particularly newborn), please refrain from distracting them to ask questions of any type (particularly stupid ones). Smile at them. Nod. Then GET THE HELL OUT OF THEIR WAY.
Now you know. Go forth and share your knowledge with the world. Class dismissed.