Relationship Commitments in a Blended Family?

I've been in a long term relationship (almost 9 years) with someone I love very much, but I don't feel as if we are going anywhere although he talks about us getting engaged often. I'm okay with not getting married, after all I've been married twice, once for a few years to my high-school sweetheart and the second marriage 20 years. My second husband is in a long-term rehabilitation facility (aggressive dementia) and has been for several years now. Although, I still visit and care for him as do our children and his by a previous marriage, I felt I needed to do the dating thing again, after all, I'm only 45. My children were totally in agreement with my decision and we communicate about everything.

While I wasn't pursuing dating aggressively, I met a gentleman while away with my job training. Me being from the South and him from up north, we were totally different, but something pulled me to him and he eventually moved south to be here. I guess I fell for him before knowing his history, but he had been married five times which I felt was excessive at an early 50ish age. There's 15 years difference, but we both were very independent professionals with no children at home (all grown). He has an adult son up north, a daughter in the mid-west and one of each on the west coast, by two different marriages (1st and 2nd).

We bought a home together about five years ago and although my children have accepted him and respect him (because they love their mom) and it's also the right thing to do, after all, they are grown with their own families. When my children call to say hello, they also ask him as well. When they invite me to outings, they also invite him.

He and I have gone on several trips up north to visit his family and son/family and they too have come here to our home as has his daughter out in the mid-west, but the two grown children on the west coast don't even acknowledge that I exist, have never met me in person and have never said anymore than, "hi how are you?" when they call their dad, if they go that far.

I've sent gifts on birthdays and Christmas, have sent gifts for the births of their children and have done everything to try and make them feel comfortable with me to no avail. He visits them at least once a year, sometimes twice and never stays out there less than a month. While there, he doesn't answer any of my calls or texts, but will call me maybe once a day, during the early morning hours before they are up since there's a three hour difference between us.

Now their mother still lives out there as well and I certainly feel that's the reason. I often see posts on social media with them all together on outings and captions "the family together" as if I never existed. Am I bad to feel hurt? In the nine years together, I've never been asked to accompany him or even asked if the dates he chooses to fly out are okay with me. He almost always has his phone on himself while home, but while out there I always get the excuse "my phone is gonna die" or "I have no coverage". It's hard with him gone for such a long period of time and not speaking to him or getting him when I call. I've tried to talk with him about this and he blows up. I feel like we are continuing on a dead end road and this will never change.