According to Wikipedia it claims that Jerry Seinfeld married a woman who was already married to a man without her getting a get from the man she was previously married to, so wouldn't that make Jerry Seinfeld's kids mamzerim?
closed as off-topic by mevaqesh, Noach MiFrankfurt, Isaac Moses♦ Mar 3 '17 at 14:43
This question appears to be off-topic. The users who voted to close gave this specific reason:
- "Questions asking for a practical ruling (p'sak halacha) are off-topic. For practical advice consult your rabbi. Try to broaden the question so it applies to a wider audience, such as by asking what sources are applicable to the question. (More information.)" – mevaqesh, Noach MiFrankfurt, Isaac Moses
I don't know anything about this person's particular situation.
For theory's sake: the product of an "adulterous union" is a mamzer. It would have to be a Jewish woman who was still married according to Jewish law to a Jewish man, and then has a child with a different Jewish man. And even then, only if this specific child was conceived "adulterously."
If the marriage between the Jewish couple did not follow halacha, many rabbis (e.g. Moshe Feinstein and Joseph Soloveichik) would use that as a leniency to not declare the offspring a mamzer, arguing that the mother was not really married to the first man.
It's fortunately thus fairly rare today.