A little background- My parents separated in early 2010, and divorced mid-2012. In late 2010 my Dad started seeing a woman and eventually moved in with her. Although I like her, I barely know her family. I haven't even met all of her kids. We have done nothing together as a group, and the one 'family' dinner I attended (without my 2 sisters) made me feel like quite the interloper. You see, my dad's girlfriend has a ton of family in the immediate area, so my dad sees all of them weekly. He sees my two sisters and I about 3 times a year.

My dad just called to tell me they are going to Vegas in June to get married. It was a bit of a shock. He had never mentioned marrying her before, and I assumed they were content just living together. So, as immature as it may sound, I'm pissed and upset. I do not know this woman's family, they (my dad and gf) have made no effort for us all to get to know each other, and I know it sounds like a 10-year old thing to say, but I feel replaced.

Does anyone have experience with blending families later in life (I'm 25, my sisters are 20), and any tips on how to be more mature about this? I'm sure I'll feel better tomorrow, but you bees are always good for a pick me up. Thanks