Another Half Sibling?

Traded emails last night with one of the moms of our two known half siblings. It appears that on the sibling registry maintained by the cryobank there may be a listing for another sibling we were not aware of. 

I had not seen this sibling on the Donor Sibling Registry but then again I have not logged in there in a while. Thought there I had set up an auto email when siblings were added. 

Interesting if true but why would a parent post on the cryobank registry and not the DSR?

Wild.