Boyfriends attitude towards me re: new neice?

My boyfriend of 4 years has just become an uncle for the second time YAY!! While we are both extremely excited - I cant help but feel a bit hurt by his attitude towards me regarding the situation. He purposefully emphasizes 'she is MY neice' or 'I'M an uncle it's exciting for ME'. I am very close to his family; his mum, the babies mum, his brother, dad are comfortable calling me Aunty Sophie - not that I really care, I know I'm not the babies blood relation, and I havent married into the family YET but it's not like i dont love it any less- it's more the fact that he makes a point of telling me I'm NOT its aunty. I feel like he is going out of his way to try and exclude me. I dont know whether to say anything to him because I dont want to look like an attention seeker and put a dampner on such a joyous occasion.