I Feel Showing Favortism

My boyfriend's daughter and our daughter sadly have the same birthday. Thing is, he's put way more effort into his daughter's sweet 16, than he is to our daughters 2nd birthday. He's gonna one party during the day(our daughters) and the other one the evening/night (his daughters). I suggested they have their parties together since they are siblings and he laughed at me saying "Tell a 16 year old she has to share a party with a 2 year old and see how she reacts". He seems to just be going all out for his daughters birthday, while for our daughter its just a cake having family over. His excuse is "She's not gonna remember it" and that 2 year olds don't really do anything. He is doing it paw patrol themed because she does like that. When I tell him he isn't putting as much effort he tells me "Then you plan the party. If you have a problem with how I'm doing things, you go plan it". And he said it super annoyed. I feel like he is obviously showing favorites. Am I overreacting? Because I genuinely can see the difference in the two parties.