Want to travel with out my family

ok, I'm a 43 year old, in a 10 relationship and we want to travel. When we took our first trip together to Italy, my mother and sister flipped out. They talked about me not asking them to go to the entire family, and they were mad, and pouted. They both even cornered us and asked "why weren't we invited" and "why cant we go with yall" making us both feel very uncomfortable. I love to travel and so does my fiancé and we want to spend our time together, why doesn't that make sense to them? Or is that selfish? We have not taken anymore trips in the past few years because of this and now are realizing that we cant allow my mother and sister getting mad keeping us from traveling. We have decided to travel to Europe this year and it has already started again. I mentioned it and my mother just came out and just SAID she wanted to go and to let her go. I offered to find her and my sister a trip and help them plan one, but that we were going by ourselves and now she is saying that "they want to go with us", "they don't want to take a trip or go without us" and "when are we taking a trip." Help-- what do I do

It's not so much about your mother and sister wanting to go with you, it's the way they go about it trying to achieve it which is causing concern. You're correct, you can't allow their angst to dictate you. You can however, sit them down and discuss with them why they feel this way. That way you will find the true reason as to why they get upset about it. When you find this reason, then all concerned have the power to negotiate an outcome which should be a win/win situation for all of you.