Avrahom asks:
If there is no safeik that the Dam is Dam Nidah.
If they are all sleeping on the same mattress aren't two of them a Rishon for simply being on the same mattress as the Av ha'Tum'ah?
Avrahom , United States
The Kollel replies:
Dear Avraham,
You are right but the Gemara is only concerned if she is forbidden to her husband, like nowadays.
All the best, Reuven Weiner