I would think that if he explain how you met, tells them how he feels about you to them and you also tell them how you feel about Tristan first, and THEN tell them, it might go easier.
I mean, if you love him, and he loves you, who are they to say your relationship is wrong? Most family members want their loved one to be happy.
Be ready to have some youtube videos explaining what trans is as well. And to answer a lot of questions too.
Let us know how things go, okay?
And either way, good luck!
Ryuichi
Sent from my SM-G930P using Tapatalk