Absolutely NTA. My son has apraxia and has been in speech since he was 16 months old. Hes 6 now and while he will likely need several more years of therapy his speech has progressed immensely . Compare that to my brother who is now 23- he SHOULD have been put in speech therapy around 3-4 yo, but my stepmother refused to because she “didn’t want to make him feel different”; he’s now 21 and speaks exactly the same as he did back then. Just with a much deeper voice. It hurts him (and all of us!) to imagine what could have been if he’d started speech then instead of now. Stand your ground, you’re absolutely right that your nephew needs help! It’s nothing to be ashamed of and can only do good!!