How do I start without my parents noticing

Hi all!
It’s my first post here so I’m a bit shy about what I’m about to explain 0///0
The point is that I want to start hrt, but the issue is that as far as I know the outcome u have with hrt depends a lot on genetics, and the main problem is that I don’t want breast, at least not as long as I live with my parents and sister(they’re both tranphobes). And apparently both my mom and sister have relatively large breasts, and I was thinking “if they both have large breasts, then the possibility of me having a relatively big one, is high”, and having a breast as presenting male in my country (Italy) is not exactly safe, and it would make employment difficult, and in my case is already harder bcz of the stigma around the issue.
I heard about SERMS, which is supposed to be a sort of hrt that based on the individual needs of the person, can be modified for various results, for example, there’s a serm hrt that doesn’t grow breast, or at least the growth is minimal compared to conventional hrt.
I’d want to know your opinion on this.