Hey JD, I haven't posted for a while but this is important.
First of all I don't think any of your feelings are unjustified, this is the only person you have been able to rely on your whole life who has wanted nothing but good things for you.
I really believe you should bring this up with your T, knowing him as I do, through you I think he probably does want to talk to you about it and maybe just hasn't either worked out how, or when. Because this is his stuff and it's never been his style to put his stuff out there.
Don't this fester, also I wanted to add I raised my ex partners kids along with my own, I didn't love or care about th any less when partner an I had kids of our own. Nor did I care about our baby more.
Your Doesn't strike me as the sort to forget about you guys have worked so hard together it's not something you can simply replace.
I know jealousy doesn't simply disappear, but I promise your T will still make mistakes like all parents do. Often times not being related but in stones care can be the better place to be.

Take care.