'She said that Irish passports, with membership of the EU, would probably be among the most covet­ed. For decades, unmarried Irish mothers were coerced into giving up their children for adoption in Britain.

A spokesperson for Ireland’s Department of Foreign Affairs confirmed would-be Irish citizens have already started using DNA evidence to help prove they are entitled to Irish citizenship through a parent, and that this evidence is submissible in passport applications.'

https://www.theguardian.com/science/article/2024/aug/18/rise-in-dna-tests-used-to-claim-citizenship-of-other-countries-brexit-eu