Fiance (40M) and I(30F) have been together for 5 years. We travel to different places/countries every year, at least 2 times per year. He has a daughter(18) and a son(15) and they always go with us. The only time we traveled by ourselves was on our second anniversary or for work related trips. This year we want to travel to Colombia with other two couples, one of the couples are childfree and the other has 3 kids (4,8,18yr). Our friends with kids won't take their kids to CR, but my fiance insists on taking his kids. If this was any other trip I would be ok with that. But this time our friends are going with us and not taking their kids. Besides that, in every trip the 15 yr old never wants to do anything, and keep complaining that he wants to go home and play video games, and the 18yr old compares everything we do to the trips with her mom, like "yeah this is ok, but that time we went to..... with mom was way better" or "I can't wait to come here with mom, or go to ..... with mom". At this time I just want to take a break from that and have a nice trip with my SO and some friends, without any kids around. Am I being an asshole? Or how can I tell my fiance without making him think I'm rejecting his kids?