Oh hun, what a terrible terrible loss and such a dreadful shock for you all.
It will be very hard for you all, some times will be worse than others, being there for each other will help ease the pain. You'll naturally want to be strong for your dad now but don't bottle up your own pain in doing so. Remember your mum with love, talk about the good times and how she was and that will help you get through this awful time. Remember, your mum would want you all to be strong.
I'm just so glad that your mum knew you loved her because you told her. We never mentioned the word when I was a kid, and when dad was dying I got there too late and never got to tell him how much I loved him (I was young like you, 24, (22 years ago now)) and that's been one of my biggest regrets in life. Now, I tell my kids I love them all the time and they tell me.
My heart goes out to you and your family.
Sending you much love and remember we are here if you need to talk.
Deb379