My Brother and his wife don't like me yet, (I think out of obligation) give my son and I a Christmas gift.Should I accept it?

(Apologies in advance for the volumous text in this question)

Increasingly, for some reason I am not aware of, my brother and his wife have ignored responding to friendly emails from me, do not thank me for sending them birthday greeting etc. and ‘forget’ to even send me an email my birthday annually.
When I used to see them at Family functions, they’d avoid talking to me. If I’d go to talk with my brother, he’d seem very ill at ease and almost looking over my shoulder to make sure his wife does not ‘catch’ him.
My brother and I always got along in the past and nothing that I am aware of has transpired to change this fact.
Nevertheless, something clearly has changed.
I’ve asked many times in the past what the problem is that he was not responding to my emails and—was reassured by my Brother that nothing is the matter.
When I used to extend myself to them and make the phone calls to see how they are, they’d answer the phone in a sing-song voice then, upon hearing it’s me, their tone of voice would be one of disappointment.

A bit of background. I am a professional portrait painter who is writing and illustrating a book about the personal lives of the 1970’s XXX stars. It’s not a debate of pro or against ‘porn’. It’s about the people behind it;with intent to expose their humanity.
It is from a journalistic standpoint.no nudity or sex talk in the book.
Just as National Geographic journallists willl cover topic matter about atrocities of war, does not mean they condone or reject war. It’s just a candid exposition.

My brother and his wife:They are muscular Christians.
I am not into organized religeon…but I am not anti-religeon either.

I believe everyone has thier own right to celebrate their faith and choose for themselves and I am very respectful of everyones’ choice in faith.

Point being People, we’re clearly living our lives differently and fairly making our own choices.
I can even understand and accept if the making of my book has anything to do with their reticense in communicating with me.
Nevertheless, we are still related.

They don’t think art is of value.
Thus-they do not understand me or the life I live.
That’s OK.

Everyone’s different and it’s fine they don’t understand me.
It is admittedly somewhat hurtful they do not elect to communicate with me but I have learned to accept this fact.

So here inlies the problem:
It’s Christmas time.
My Parents have informed me that these 2 people who can’t be bothered to relate to us on any level have bought gifts for my son and I.
Am I obligated to accept these gifts and issue a thank you – thus encouraging them to continue this-what I see as insincere issuing of gifts to US: the people they can’t be bothered communicating with?
I feel like they are treating me-the proverbial starving artist-like charity and it rather bothers me – this notion of accepting gifts from those who I can’t afford to buy back for and moreso, accepting gifts from those who clearly do not like or respect me.
It is in my nature to respond – if i were to accept the gift- with a ‘thank you note’, albeit curt and impersonal at this point.

My question is: Should I even accept these gifts?
What would YOU do?

Thank you for your time in reading my query.