Your post is very confusing and does not have enough information. Are you your daughter's bio mom! If so, do you not have an idea who he might be? Perhaps you are able to identify these two men as possibilities because you know the father's name? Why are you focused on them alone.
Do you know the aunt or you think she's an aunt because of ancestry.com? Have you sent this message to a stranger? How do you know she received the message?
Why haven't you or your daughter contacted the two men directly? Why do you think they're half-brothers? If I were possibly a half-sibling, like you think these men are, I would not take a DNA test based on a stranger's request. I would expect to be shown a history showing why you think I am a sibling.
Brings up another question. Do you think they are full siblings? If so why?
Does your daughter have a copy of her birth certificate? If not, she needs to apply for one from the state in which she was born. She can apply on the Internet. Has she talked with the hospital asking if they have more information. They may not because of the length of time. Does she know her birth father's name. Did he sign away his parental rights? If so, there may be a file with that information.
Have you talked with a professional person about how to search for her father. There are people who will help you search. If you have good reason and not just a hope that these are her brothers I suggest the next step is to talk with an attorney about what you can do.
I wonder what you and your daughter have tried for the last 30 years? The longer one waits to do research the more difficult it will be. Have either one of your searched through newspapers near the time and in the area in which she was born? What are the circumstances around her birth? Might there be a birth announcement in the newspaper? Who were her mother's friends and relatives at that time? Have either of you talked with them? Follow up mail with a phone call.
I have a friend who was given to an unrelated couple immediately after birth. She was norn in a small community. She learned the circumstances of her birth by talking to the doctor or perhaps a nurse who attended her birth. When and where was your daughter born? Is it possible someone who might have been around then to be alive and willing to answer her questions?
I feel that there is much more to your story that is crucial to know what might help.
I reread your post and am more confused. Are these 2 men her aunt's brothers or possibly your daughter's brothers or one may be her father? Is the aunt your or her mother's aunt or her aunt? Do you know that one of these brothers is likely to be her father?
If you know any of the people involved then be more direct and actually talk with them instead of beating around the bush.