Shiduchim
If there is information of either side following apikores , chas vesholom ,
One needs to reveal such info. If it is not definite , they should be told to check it out.
Even if the shiduch has been completed & this info might break it up , it is still a Mitzva to reveal this.
Now may be a good time for a gem of Torah study.
www.GemsofTorah.com