On June 20, 2011 a routine ultrasound changed my life. I heard five words that I never in my wildest dreams thought I’d ever hear, “Well, for starters, there’s two.” It took 30 minutes to get from the doctor’s office to my mom’s work. In utter shock, I typed TWINS into the Google search bar on my phone.

From that moment on, I’ve relied solely on knowing every factual piece of information I could about my condition.

Now I find myself being approached by complete strangers asking the most obscene questions and making not-so-hilariously obvious comments. The phenomenon that is my life can easily be explained by doing the same research I did but it’s understandable why no one ever looks into it. It’s not really a topic the average person thinks they need to be an expert in.

Today though is your lucky day. I’m sharing with you some little known facts about twins.

There are two main types of twins: Identical and non-identical (commonly called fraternal). Identical twins share all of the same DNA factors. Fraternal twins are no more genetically alike than any other pair of siblings. Fraternal twins can have very similar looks just as two brothers or two sisters would though. Identical twins are not clones of each other. Environmental factors can change the appearance of each member of the twin set. Identical twins will have the same natural eye color, hair texture, voice patterns, colics and genetic medical conditions as well as the same blood type.

To save time, I won’t discuss conjoined twins but just know it’s also a rare possibility.

Twins are carried in one pregnancy in one of three ways: they can have separate placentas and separate amniotic sacs (dichorionic diamniotic or di/di twins); they can share a placenta but have separate amniotic sacs (monochorionic diamniotic or mono/di twins); or they can share both a placenta and an amniotic sac (monochorionic monoamniotic or mo/mo twins). The two latter options always result in identical twins. This means the twins will both be girls or both be boys. The first though, the mysterious di/di twins, can be either fraternal twins OR identical twins. 75% of the time, the twins will be fraternal. 25% of the time though, they will actually be identical. This is likely the most confused concept in the twin world, even among medical professionals. Let me repeat just in case you did not catch it. Is is possible to have no idea if your twins are fraternal or identical. A few obvious things may help you figure out which category your twins belong to including gender, blood type and overall appearance but if your same gender twins are still too close to tell, a DNA test will be the only way to know for sure.

A set of twins can be one of three gender combinations: boy/boy, girl/girl, or boy/girl. Boy/girl twins are NEVER identical. No matter how close their appearances are, there is one very, very big difference. Same genders twins though are not always identical. If your same gender twins have very distinct looks, you can safely bet that they are not in fact identical. If they have different blood types, different eye colors, different hair patterns, etc. they are not identical.

In less than 1% of twin pregnancies, a semi-identical set of twins forms. This means the mom’s egg splits early during ovulation and is then fertilized by two different sperm. In this situation, any of the gender combinations can result. The twins are not identical but they share at least half of the exact DNA so they aren’t really non-identical either. Some examples of semi-identical twins result in mirror twins or polar twins.

There is a 0.3% chance of spontaneously conceiving identical twins. You are actually more likely to get pregnant while using any form of birth control (which typically comes with a success rate of 99.4%) than you are of conceiving identical twins. There is no genetic connection. You can be a twin, the daughter of a twin, the son of a twin, have 10 sets of twins in your family but there is still no genetic connection when it comes to conceiving identical twins.

The chance of conceiving fraternal twins is somewhere between 1.7 and 5% (and upwards of 20% if fertility medicines and procedures are used). Fraternal twins make up nearly 75% of the twins in the world today. Several factors impact conceiving fraternal twins including age, race, and family history.

Your husband’s family history does not matter. The father contributes the sperm. That’s it. Nothing about that sperm can make a woman’s egg split or make a woman ovulate multiple eggs. There may be plenty of stories saying otherwise but I promise you they are coincidence. You be sure to show your mother-in-law this post, okay?

And dads, just because your genes had nothing to do with it doesn’t mean you don’t play a part. Men with stronger or higher than normal sperm counts are more likely to conceive twins. (But that doesn’t mean that all twins are conceived because of this reason.) There’s a popular dad-of-multiples saying, “Real men make twins.” It’s not appropriate and really rude in the eyes of men that may have medical issues preventing them from conceiving but unfortunately, the joke that is implied has some fact behind it.

There really is an abundance of information just waiting to be learned about twins. Feel free to ask me more or start some research. Who knows, maybe you’ll find yourself like me one day, shocked that it happened to you.