Pitching a Tentacle by Lilo Quie

Cane had always been a good cecaelia, kept his tentacles to himself, and left the omegas alone, but when the king’s son professes his love for him, Cane can’t commit. He waits for his fated mate, even if the king will punish him for rejecting his son.

Morgan has lived a quiet life in forced solitude learning the manners and quiet duties of an omega. Dolphins are polyamorous creatures, and Morgan dreams of being touched by multiple hands at once, but his family has other plans for him. When his arranged marriage to a wealthy beta goes sour and he’s left marked and devalued, he flees his home and asks the council to remove him. It’s there he learns it’s not multiple men he craves, but the multiple arms of the hottest cecaelia he’s ever seen.

Together they find love and family in the most unlikely of places. Even with the little lost merboy who needs a family, no matter how much he wants to believe he’s part piranha. Together with their pet lobster Bluecifer, they’ll be the family that none of them ever had.
Warning: contains shellfish.