www.google.co.uk/amp/s/www.nbcnews.com/news/amp/ncna891836
A theyby is, I think, different things to different people,” Nate Sharpe told NBC News. “For us, it means raising our kids with gender-neutral pronouns — so, ‘they,’ ‘them,’ ‘their,’ rather than assigning ‘he,’ ‘she,’ ‘him,’ ‘her’ from birth based on their anatomy.
On another site he was quoted as saying “we don’t tell anyone their gender... not even the children themselves” 
The (twin) children are 3
Has this been going on for ages? I’ve never heard of it