So me and my youngest son dad have joint custody and I got my ds a kitten cause he asked for one for…

So me and my youngest son dad have joint custody and I got my ds a kitten cause he asked for one for Christmas. When I called him I told him he was excited and now my ex wants me to transfer the cat with my son. Like wtf? If you want him to have a cat at your house buy one! So when I have his sister (not the ex's) will you want me to let you have her over too? Really!