Wow.

I've read through this post and it's quite a story.

I think you found a very gentle, caring natured person.

The problem is, he doesn't know how to put your needs nor his needs in the relationship first and seems to be doing everything for everyone else.

I'm not seeing what is driving this behaviour of his. Why he has the absolute urge to help them all the time. Are they quite a bit older than him? It sounds like he has taken on a "parental" role with them. It's quite strange.

Honestly. I would not want to come second best to someone else with my partner. Him making plans with you and cancelling because they ask him something and he clicks his fingers and goes running, is not okay.

If he's not able to compromise - nothing wrong with helping others out - but not at the expense of your time / commitment / plans together - then this is not the type of relationship that I would personally want to be in.

You deserve to be cherished and put first.