Its a little unusual as we like to keep the past firmly in the past.
But I can appreciate what you are saying.
My partner has no living close family so for me this is not an issue.
But if he did, and they were to meet my family,
It's pretty certain that someone my side, at some point,
would use the incorrect gender term for me.
I still wouldn't want my partner to tell his hypothetically still-alive-family, about me, though. But that's just me.
I've a friend, Jane*, Ts f2m pre-op.
Through her I've become very close to her mum, Elizabeth*, who I now thing of as my second mum.
Elizabeth refers to Jane, as Jane, but quite often reverts to Jane's previous name, Ben*, then backwards and forwards, without realising it.
So I can see where your Ex is coming from.
Revealing her past is her decision.
She wanted you to share this info, with your family.
While having a relationship with a Ts woman is not in any real way analogous to a M2M relationship, some people struggle to accept this fact.
In your description of your family, you talk about gay members of the family. So you having a Ts partner is not going to be a complete unknown thing for them to accept.
Plus they already know her and like her, so there is no great leap of acceptance for them.
Stop over-analysing things.
You sound very committed to both her as a person with her ongoing changes,
as well as having a more fuller ongoing relationship with her, like you both used to have together.
I'm sure you would want to, in your own time, tell your family. But you have to be ready.
Are you able to do that?
Maybe ahead of going back into a full blown relationship with her.
"I've been thinking about all the things you have said. Yes you are right. Whether we are a couple again or not, I would like to tell my family about your trans history. Would you still wish me to do this?"
Oh, Jane has a long term partner Nigel*.
Jane was considering detransitioning. {she didn't in the end}
I asked Nigel how he felt about that.
He thought briefly then said:
Well I guess I'd then be in a gay male relationship.
I asked my man the same question; his reply was the same.
*made-up names but the rest is not.