I like to think the people who know that Maggie Sr was Eb’s daughter are on the Gray Council since he clearly trusts these people with some of this most intimate secrets. Eb seems to be a founding member of the GC, so it would make sense that he fills it up with the Wizards he trusts the most.
So far it’s just Odin & Rashid, but given the posse he brings to meet Harry before the White Council meeting in SK, Martha Liberty & LTW might also be part.