DDs DF and I split about 3.5 years ago. He has taken her abroad in the summer 3x in that time - twice alone and 1x with his new 'family' (GF who was pregnant at the time but recently had the baby).
Ex and his new GF have been away on 1 holiday without DD (she's 10 btw) before she was pregnant and a couple of long weekends without DD too, which whilst DD missed him it's not a family holiday so to speak.
DD came home last weekend quite upset that DF, GF & baby were going to go on holiday next spring without her. They said that they will take her away in the summer holidays but not the spring holiday 1. because it's in school time and 2. because they want to go for 2 weeks and DD gets homesick (she's been away with DF for 7 and 10 days before and got homesick both times).
Whilst I agree 2 weeks is too long, AIBU to think that they shouldn't go with baby but not DD, regardless of whether they take her in the summer? Can they not go for a week over easter or something?