Is it ok to feel mad/sad because of this?

So I just got my Christmas gift. It is an iPhone 5C from my parents. I was very excited when I got it and gave them a huge hug. But the next day, I noticed that my sister got an iPhone 5S.Me and my sister are twins… Now I feel kinda mad/sad cuz that would mean my parents likes my sister more than me to buy a more expensive phone (with some cooler features).

Is this feeling ok to have? Or am I being ungrateful?

P.S.
My brother ( who is older than me) got an iPhone 5C as well.

My sister said she wanted a green 5C.

My dad in a computer engineer and researches electronics before buying them.

Did the opening screen say "you're adopted!"?

You should be grateful, I just found out this morning while we were opening presents that my cat was walking weird and not eating. My present is that we will have to put my cat down tomorrow because we don't have the money to fix him.

Could be there was only ONE 5 s, in which case that should have gone to your brother, since you and your sis are twins.
However, with twins and identical phones, life could be complicated.

I didn't get any Christmas presents. Should I feel mad or sad about this?

Dude you got an IPhone. I know it may seem unfair that your siblings got a better gift but honestly you got a better gift then I did. Be grateful, be happy. Use your IPhone and move on with the jealousy. Hey, at least you got a present. Many kids and adolescents, this year, will get nothing because of financial cost.