Please read the following text and answer the questions.

Granpa's Birthday

    It was my Granpa's birthday last Sunday.

    On Friday, my sister and I went shopping. We found a nice Batik shirt. We bought it and wrapped it in a blue paper. Blue is my Granpa's favourite colour.

    On Saturday morning, my brother and I were in the kitchen. We made a birthday cake. It was big and beatiful. I wrote Happy Birthday on it. We put some chocolate on it and a big candle on top of it. On Sunday evening, we had a party. My uncle and my aunt came to my house. They brought some cakes and flowers for my Grandpa. We sat together in our living room. My dad said a beautiful prayer. Then, we sang "Happy Birthday" and my Grandpa blew out the candle. He cut the cake and gave it to everybody in that room. He opened his present and he was very happy with the shirt. 

    Finally, my grandma told us some stories about my Grandpa.

How many siblings that the writer has?