I don't believe making my genome available, which contains similarity to my relatives, is a breach of their privacy.
I think part of my point is that DNA, by its nature, simply cannot remain confidential, and that thinking we can keep it that way is just going to lead to inevitable disappointment.
First, some people extend your argument from DNA to everything and say "I believe that privacy in the modern world is unrealistic"; that doesn't make the argument applicable to the rest of us.
Second, whether DNA can or cannot remain confidential is yet to be seen, but feasibility is certainly orthogonal to whether it ought to be, which is the point at hand.
Third, whether you believe it's a breach of privacy to leak part of your relatives' DNA is besides the point. It's their decision to make, since it's their personal data and deemed confidential under most privacy frameworks, and therefore a breach.
To your first point: Yes, I generally extend my argument to more or less everything in the modern world. Put your garbage out on the street: reporters can rifle through it looking for evidence.
To your second point: we already know DNA can't remain confidential (there is no practical mechanism by which even a wealthy person could avoid a sufficiently motivated adversary who wanted to expose their DNA). That's just a fact, we should adjust our understanding based on that fact.
Most important: sharing my genomic information with the world is not a breach of any privacy framework I'm aware of and subject to (US laws). Do you have a specific framework or country in mind?
I think part of my point is that DNA, by its nature, simply cannot remain confidential, and that thinking we can keep it that way is just going to lead to inevitable disappointment.