I’ve never put much stock in the theory that Ariel and Eric could be Hook’s parents. Seems highly unlikely IMO, my Hookriel shipper sensibilities aside. I just don’t see them having another character apart from Emma also having a long lost parent being the same age as them, which is where they’d have to go with it if they plan to have Ariel as Hook’s mother in present day. That would diminish Emma’s uniqueness, and I really don’t think they’d go there. And I also can’t imagine them waiting this long to show Ariel, only to reduce her to a supporting role in Hook’s flashbacks.
After the casting call for 305 came out it did sound potentially like “Liam” could be Killian’s father and/or Eric. The description of a dark haired sailor could fit either of those characters. But then we heard that Eric is being cast for 306, so even if Liam’s related to Killian, he’s not Eric.
Someone posted on tumblr, the casting call info for Eric, accompanied by a gravestone with Hookriel written on it. Charming. Pffft. Thankfully someone replied that that was uncalled for, because we actually have no idea how Eric is gonna fit into the storyline yet, so the mere fact he’s gonna be there in some capacity, doesn’t actually rule out of the possibility of Hookriel.