A mate bond. The bridge between two souls, a connection of minds and hearts. A rare enough phenomenon, but a mating bond between three? rarely heard of.
Feyre and Rhys had known you were their third the moment you stepped into their home with a shy smile and gentle air to apply to become Nyx's nanny. The bond had snapped the moment you held their child in your arms and promised to care for him like your own.
They decided not to tell you, it was clear you were oblivious to the bond and they didn't want to frighten you. They also wanted more time to make sure you were dependant on them and couldn't leave.
The rest of the inner circle were informed, they were family after all, they needed to help. Everyone but you was aware of the bond, everyone helped block you into their lives. From Mor coaxing you to stay in the home with them all and filling your room with things you like to Elain and Azriel teaching Nyx to call you Mama. They were all in on it.
Rhysand and Feyre were content to bide their time, watching you adoringly and waiting for their moment to strike.
As you sit on the patio cuddled up with Nyx in the gardens, the inner circle watch you from their perches. You are good as trapped now, nowhere to run, no one else to rely on.