Our stories are very close. Both my grandfathers are dead but both my grandmothers are living. I don't see or talk to them very often since they live far away. They have both commented on my deeper voice. One thought nothing odd of it, but she has early Alzheimer's. We're thinking there's no rush in telling her because it would probably massively confuse her anyway.
I talked to my other grandmother on Christmas and she was concerned I came down with a terrible cold.

Anyway, she is very religious and one of the biggest haters of my "tomboy" childhood. This woman tried to "get me out of my rut" and force feminine things on me unlike anyone else- especially during my teenage years. Despite all this I love her alot.
My father, stepmother and I have been racking our brains about how to tell her. There was no huge urgency but now she's coming to visit this Thanksgiving.
My father thinks telling her as little as possible is best. He mentioned he might tell her my sexuality has changed and I started binding. We all agree my top surgery is something that's best not known with her. However, I do believe she'll notice my deeper voice and I now physically look like a guy (duh).
She's in her 80's and I don't know how much she knows about transgender or transsexual issues, but she's not stupid. She does know about "sex changes" and that changing your sexuality and wearing just men's clothes doesn't cause physical changes like T does. I also can't help that I think if she found out she didn't know the truth she would be more hurt about being left out. Yet, this woman is very stubborn and a force to be reckoned with. This is evident when men in their 30's and 60's are concerned about her anger and backlash from this.
This is what I hate most about transition- telling people. I've been pretty lucky so far, but you never know how someone will take it and react.