Mildly annoyed. It's my SOs birthday so I'm picking up food and I baked him a cake. His mom and…

Mildly annoyed. It's my SOs birthday so I'm picking up food and I baked him a cake. His mom and sister are coming over and she's also bringing a cake. It's his birthday so why are we paying for EVERYONE'S food? His mom, his sister and his cousin. Any other time I wouldn't care, but his birthday. What the heck?