The data being made available on Genes Reunited (date of birth, name, etc) is likely already in the public domain and hence is not covered by the data protection act.
I could for example search the electoral role and find the same information about you.
Relationships between your relatives are also likely to available to the public already were to spend time searching for birth/death/marriage certificates.
Assuming that the information was not in the public domain and was covered by the data protection act there may well be a breach, but this breach would not be by genes reunited as they did not make the data available. The data has been made available by the person (or persons) who uploaded it to the genes reunited site and told the site to make it available to others.
I don't think the data protection act is being contravened in any way.