I can so relate to your situation. The only advice I have to offer you is to follow your gut. If you want to reach out to your mother's estranged siblings (via email since you live in another country), then you should do so.

The fact that your parents and the rest of the extended relatives want to pretend the estrangement between your mother et al doesn't exist, is never going to change, unfortunately. It is definitely a charade and it sounds like your family culture is one of denial rather than open expression and honesty.

I'm estranged from several members of my family and as a result, know that I have nephews and nieces who will never know of my existence. I offered several olive branches ("let's attend family therapy to sort through our issues with each other") and was rejected. I too, come from a family culture of denial. It's much easier for my family to put on a charade of "everything is just fine and dandy" when it certainly is not.

I have emailed several family members whom I'm estranged from, to explain why I chose to distance myself from them, and explain what my conditions are, for them to follow, if they ever want to resume a relationship with me. They have yet to respond.

So, my family of origin is dysfunctional but I haven't let that stop me from seeking out emotionally supportive friendships that are healthy and as close as a family should be. I say, don't limit yourself to your family of origin. Seek out support from others elsewhere in your life. If your family of origin want to act like imbeciles and stay in denial and stalwart your efforts to repair broken communication lines, then original family be damned! They sound like stubborn fools, but that could be me just projecting.

At least you are not participating in that dysfunctional family culture of denial. Don't. It's bad for your well-being to perpetuate that toxicity. No regrets. That is what life is about.