All who could have an idea of what to do with it could seek a way to get that data out of every company or gov that have it for their specific reasons, no matter if data was collected lawful or not, or if access to the data is then lawful or not.

1. search for source of evidences on crime scenes: if one of your relatives happened to have been (related to crime or just bad luck) at a place where later on some evidence was collected, you might cause trouble for them bcs your data is very similar to theirs and that is obvious to laboratories. depending on the the “later on” current state of technology it could affect relatives more than two or three steps away from you. if you live in a country where law enforcement gives a shit about truth and just seeks for one argument to punish just anyone they can point a finger at, that could become a huge problem for the whole family then just because there was data that could have been abused.
2. illegal organ traders could - once they have access to your data - think you or your relatives could be a source of nice income if a client of theirs happen to pay enough. however you will probably never know as the illegal organ traders are unlikely to ring the doorbell to ask nicely for a contract. How much do you think would a richie in personal needs pay for “spare parts” if those who deliver them wants him to just never ask where it came from ? does it matter if such organ teaders could know a “compatible match” by data only? maybe not because they might know tomorrow or someone might put up an AI to do the matching (does it matter if that matching by AI is correct then? i guess such traders don’t really care and their customers probably, but wouldn’t that be possibly too late then?)

For me the latter is actually enough to not willingly give my DNA data to anyone. for no reason. gov might already have it (covid probes had been collected and frozen at least) but actively pushing your data out inzo the world would be insane IMHO.

Laboratories often use Microsoft Windows, Microsoft Active Directory and Microsoft Exchange, thus i personally see no reason to NOT believe that any data they have received once in time would - sooner or later - end up rotating uncontrolled in the hands of uncountable criminals waiting for any chance to make quick or huge money out of it.