Where there is a physical condition such as a DSD, there may be justification for a physical intervention, though the least invasive would nearly always be my preference. When there is no known physical problem, it is unusual to say the least to consider a surgical solution. In the case of a hormonal imbalance, I would expect an endocrinologist to prefer a subtle adjustment over a drastic change to the body's workings. It is really worrying when a ideological position is taken that says people have a right to do whatever they like to their bodies, facilitated by doctors. We do not treat people with gender issues the same way we treat people with other psychological problems.
Familial impact is very real. It is caused by a number of things. First, it is a shock when someone very close to you says that they are really someone else, not the person you know and love. That in itself may take a long time to come to terms with, but certainly in my case my immediate reaction was to assure my son that I will always love him.
Secondly, the familial impact is heavily compounded by the self righteous activists and allies, who think they know everything. When someone imposes their self perception on everyone around them and demands that they be treated as if their self perception is reality and everyone else's perception is wrong and comes from bigotry and hatred, there is a big problem.
Other factors are the very real fear of losing a loved one to a "chosen family" who will not be there when life gets really tough, but are superficially attractive because they affirm and affirm and affirm, and the fear of a loved one going down a dangerous and physically destructive medical or even surgical path. No-one knows in advance whether cross sex hormones or surgery will cause serious physical problems, or whether it will lead to regret (a rather weak word for the ongoing nightmare some experience).
I'm glad your family listened with an open mind. So do I, but no-one has been able to present a coherent rationale as to why "gender dysphoria" or a wish to be the other sex requires us to deny that our son is my son, or why oestrogen is a good idea, or why anyone should try to change physical reality, or why our having a different (and perfectly rational) understanding of gender and sex is cause for estrangement. I'm still listening.