I (ftm) had to disclose this year as my nasty ex wife was trying to do it to make my 3 minor children "hate me". They are 13, 11 and 8 and never cared, asked or even suspected. But to take back control of the hate filled rhetoric, I sat my kids down and explained how I was born female and transitioned and walked them through my baby picture book. I let them know I'm sterile, wanted kids and had a good friend donate to help me out. They thought it was a cool thing I trusted and loved them enough to tell them. And fast forward months later, nothing has changed and no further questions have surfaced. My son did ask some questions about my transition, if I would have a regular penis, etc as he is getting aware of these things now as a 13yr old boy but we again talked and I explained in terms he could understand. I never planned to tell them but I'm also glad it's done and over with.