not a trans man, but I've been on T for 1½ years and I also live with transphobic parents. I think girlmoding is pretty easy for the most part, they just think I'm a tomboy. even now I get little to no facial hair at all, but when I do I'll just shave
what might actually give it away is the voice change. my voice got noticeably lower within just a couple months and it's been very slowly deepening since then, but I've also seen people say it took them around a year. I'm lucky that my family kind of just brushed it off, since my cadence is still fairly feminine. if you think your family will clock that sort of thing, start voice training as soon as possible (voice training is a thing you should do regardless, which I'm guilty of not doing T_T)