Mary Emma is Charlie's little sister. While she's only 10 months old now, one day she will need to understand so many things about her brother, who has Down syndrome. As their mother, I have so many things I will want to say, but I'm old and might forget by then. Here are my priorities:

My son, Charlie, is 2 years old. He has crazy blonde hair, bright blue eyes and the most incredible, lush eyelashes. He also has Down syndrome.

The Husband and I knew we wanted more than one child, and when Charlie was born, we understood how helpful it would be for him to have a sibling close in age.

Being Charlie's sister doesn't mean you have to give up anything.

Mary Emma was born 17.5 months later. She has dark, curly hair, bright blue eyes and… eyelashes that are on their way to matching Charlie's. She has the cheeriest personality and the funniest laugh. When she was born, she sounded like a goose honking when she nursed or drank from a bottle. That slight honk carried through to her giggle. I can't help but laugh in return.

Emma -- as we call her because that will be easier for Charlie to say one day -- is almost 11 months old now. While she's too young to understand, I know one day I will sit and explain what makes her brother different from most other children.

What will I say? What questions will she have? So many things may be different by the time we have that conversation. But for now, this is what I want her to know.

I'm so grateful for you both

You and Charlie mean the world to Daddy and me. We have celebrated every achievement and milestone you each have made. We will always be proud of everything you do, because we made you.

You are special, too

Every child is special, in his or her own way. You have the most beautiful curls, which will frustrate you as a teenager. You might feel like they don't make you pretty, when in fact they make you beautiful. Charlie's extra chromosome makes him beautiful, but it also can make him frustrated when he has to work that much harder to do things you do naturally.

You still must work hard

Just because some things will come more easily doesn't mean you can slide through life. Just as Charlie will work hard, you will work hard. Part of my expectation of you is that you will never take your abilities for granted. There may be days when you want to. Charlie will remind you why you have to keep working hard. This doesn't mean you have to be valedictorian or a star athlete. This means you can never give up.

You must live your own life

I want you to experience so many things. I want you to attend the college of your dreams and pursue a career that exhilarates you. I want you to fall in love with your soul mate (P.S.: They don't exist until you're in your 30s). I want you to travel. But I never, ever want you to forget your family.

Being Charlie's sister doesn't mean you have to give up anything -- quite the contrary! You're going to find that being Charlie's sister means becoming family with people who may never have come into our lives if we didn't have Charlie. You will feel so much love as you go through life.

You were born an advocate

Being Charlie's sister means you were born with a strong social spine. It is in your blood to stand up for others (starting with yourself) and to speak out against bullying, hatred and discrimination. That may feel like a very heavy burden on some days. Know that Daddy and I love you endlessly for the strength you will show as you mature. This isn't a ticket to be rude. Being respectful is as important as being an advocate for Charlie and others with disabilities or differences.

Take care of each other

Yes, things may be different because Charlie will need us for a long time. But Daddy and I will work very hard to make sure Charlie's future is his own. I know we are raising good, kind children who will always love each other and look out for each other. Charlie may look out for you more when you're younger, and you may look out for him more when you're older.

Please be patient

Your Dad and I may embarrass you at different times in your life. (Please note, Daddy will be trying to embarrass you.) And Charlie will embarrass you. It's OK to feel all kinds of emotions, so long as you take a deep breath and practice patience. It won't always be easy, and it's OK to cry.

Let Charlie channel love

Above all, I hope you will surround yourself with caring, kind people who will want to know and love Charlie as much as you do. You will always have an easy gauge on others' character if you can see how they look at Charlie. Do they see what makes him wonderful? Do they see what makes you amazing?

We will always be here for you, and we will always love you.

Read more about special needs

One mother's plea to stop use of the 'R' word
Learn to advocate for your child with special needs
The truth about my child with Down syndrome