Anyone with any experience of jealously in a 8 year old

[prelly]

My ds is 8 and an only.
We have a younger child in the family a 2 year old girl.
My ds has moments where he seems to get really jealous of the attention that she gets from the extended family.
The little girl does get loads of attention in the way of gifts, being taken out etc.
There are times where I have had the little girl round my house and my ds will have nothing to do with here and doesn,t want to be in the same room asking me instead to take her home and then there are other times where he is okay with her and will play with her.
I do suspect that ds gets jealous of the attention everyone gives her he actually picked up on the one day we were all out and a family member bought her a balloon but didn,t buy him one as it was my mom bought him one.
Just wondering if anyone had experienced this with an 8 year old when younger members come into the family.
He can be quite nasty at times not wanting to play with her and he became really angry a couple of weeks ago as she kept calling me mom.
I know that people don,t mean to leave ds out its just how it is with a younger one.
My ds seems to also have it in his head that I myself prefer this child to him.