I am not a sibling to someone with Cp....but my 4 year old daughter has it..I am a young mother..Im 20... What ever question you have...feel free to ask me! Its a different lifestyle when you have a family member with CP...but It will be fine... How severe is his cindition...what can or cant he do? My little can not walk, nor talk, nor hold her body up... she does babble as if she was a baby trying to make out words....She very smart...we find out what she wants by asking her yes and no questions..she shakes her head in response, yes/no.
The best advice I can give you is, be strong!! You, as a big sister will have such a big impact on your little brothers life!! And im sure you already do!!
I hope to hear from you soon! Take care and Luck to all of you!