"My husband isn't my 'other half'. My big sister is."

When I was little my older sister was at the very top of a four-child hierarchy created by my parents, who let it be known that as their first child she was more special than the rest of us combined.

Until my brother came along, that is — the “golden child” (have you picked up on our ethnic background yet?). From then on, my sister and I have managed to put the hierarchy aside and begin the path to friendship.

She is my other half. Not my husband, my sister.

She’s always kept an eye out for me, but our true closeness began when we had children at around the same time and spent the next few years completely co-dependent, referring to each other as our children’s second mother.

I couldn’t have done it without her. I owe my entire career and relationship with my children to her.

It never felt like I was abandoning my children for work or anything silly like that (don't feel guilty for working, mums — you are NOT abandoning your kids by working) because I was dropping them off to their cousins' house or their cousins were coming to our house.

I would drive away feeling completely relaxed about where they were and how well they were cared for.

But that's just the beginning of the thanks I owe to my incredible big sister.

1. Thank you for breaking in our parents.

I remember that night when you and mum had a huge fight because you wanted to go to a George Michael concert when you were 16 and she wouldn't let you. Parents are always more cautious with their first child but by the third, you pretty much raise yourself.

You were pissed when mum said I could go to a Prince concert at 16 and had a bit of a rant about the fact you weren't allowed to go to concerts at the same age. I directed several death looks in your direction, but forgave you for risking my night out when you offered to take me to the concert.

2. Thanks for the clothes.

I used to wear your clothes, makeup and jewellery behind your back and I used to run for my life when you busted me. It took a few years but you eventually let me borrow some of your clothes with permission, without threatening me with death for touching them or even looking at them.

When we got older you used to buy clothes for me and all I had to do was look at something of yours and you were packing it up and giving it to me. (Post continues after gallery.)

3. Thanks for giving me a life.

The Prince concert was just the beginning. As the first of us kids to get a job and a car, you were my lifeline. I remember you driving us to the local video rental store every Friday night and paying for movies and snacks.

Later, you and your boyfriend used to take me so many places - normally with the purpose of setting me up with one of his friends or cousins - but still, at least I got out of the house.

4. Thanks for loving me, even though you know all of my shit.

You know me better than my husband does. Better than I do. You know all of my deep, dark secrets and I know you will carry them to the grave. You have never brought them up to me, even when you've been angry with me. I trust you more than I trust anyone else.

You have my back. And I have yours.

5. Thanks for knowing what I need before I do.

There are so many examples of this, too many to remember, but two that stand out to me are when I had my third child a little earlier than planned and became comfortably housebound. You turned up on my doorstep and almost physically threw me out of the house for a walk, for a jog, to go shopping, anything that would get me some fresh air. When I returned home too early you told me to go back out and slammed the door in my face.

And you sent your cleaner around to my house after I slumped on your dining table and almost cried at how the very idea of cleaning the bathroom distressed me. Who had the time, the energy? He and his team now do it for me every fortnight. My clean bathroom reminds me of how much I love you.

6. Thanks for making me a better mother.

When we became parents we were both in complete agreement about the kinds of mothers we wanted to be - but old habits die hard. Whenever I felt myself about to become the kind of mother I never wanted to be, I'd call you.

"He's driving me mad!"

"I can't breastfeed anymore. It HURTS."

"He doesn't listen to me. He's so naughty!"

You'd talk me down off the mental ledge I was on and enable me to calm down and handle all of the hard times with your words of wisdom bouncing around my brain comfortingly.

7. Thanks for trusting me with your kids.

I know how precious my children are to me and how picky I am about who I leave them with. I have always trusted you to look after my kids because I know how much you love them.

And I yours.

Thank you so much for trusting me with your children when they were so little. Sometimes it was hard to have so many little ones at once - as you well know - but it was also the best time of my life. The relationships we have with each other's children today, now that they are older, is because of all of that time we spent together and I treasure them.

8. Thanks for your carrot cake.

I never understood carrot cake. Why bother? A carrot is a vegetable and had no place in a cake, as far as I was concerned, until I tasted yours and became immediately obsessed with it.

I dream about it (hint hint, please make another one for me soon) and even though you've sent me the recipe several times I prefer yours. It tastes like love.

9. Thanks for not getting mad at me for the stupid things I say and do.

I know I've said and done so many stupid and hurtful things and I didn't mean to hurt you. You never got angry at me. On the rare occasion I was upset with you, you never let me be. You'd come over and sit in front of me until we were okay.

You are my Big Sis, my rock, my idol, my everything. You are the reason I sometimes feel sad my daughter doesn't have a sister, and neither does yours.

My dream is that they become for each other what you and I have become. The very best of sisters, the very best of family, the very best of friends.