Oh!! there are lots of Dr. Phil here :D:D .j/k (if it cheers u up then thats great)

Its really sorry to hear ur story. But i am quite perplexed that i did not see ur father and siblings role on handling that act.

As u r the youngest and u r already in states, i am assuming that they(siblings) r already in mid 20's or late 30's. But still they (ur dad n siblings) dont discuss these treatment u r getting. As u say it will be pretty obvious to them how she is treating with u, u never had discussion with them? And they don't do any abt it?

I am not the youngest and its been a while (or more than while) i am planning/participating in my younger siblings b'day party. sometimes its a party, sometime i just make them feel good by saying ur the youngest and they mean a lot to me and today is ur special day and i can do any thing for them with crooked smile on the face(so they also know I am just boasting about i can do anything for them), but they always love it.

dude have u ever confront ur mom in this issue. its ur choice (sometimes it can be a solution or sometimes u might find more dark secrets why she is giving cold vibes to u)

Now what next, thats the thing u r looking now.. i believe that the best thing is.. give ur respect and love to mom (although she might deserve it or not is a different story). And at the same time what i will suggest is that confront her... now u r already have stable life and mature enough...next time when u meet here personally.. just to talk to her personally.. tell her that.. i always feel u neglect me a lot, never ever recall a single moment where u made me special and u were proud of me .. but still with those treatments u gave me, u made me the man whom i am today and i am proud of being who I am .so I would like to thank u. But at the same times i would also like to let you know now it does not make me difference how u will treat me, now i am used to of it. But I will treat as my MOM and let me know if i can do anything for u"

At last "Never judge people until you have walked a mile in their shoes" So try to empathize ur mom and find why she treat u like the way she is doing, might because of a mental condition or just because of any other reasons"