Vincent/Molly?
I promise I have read all three threads but can't remember everything that has been posted so apologies if someone came up with this already...
Ian and his wife had a baby boy (Vincent)
Wife knew Ian was a paedo who liked boys so brought the child up as a girl (Molly) to protect him from Ian.
Ian discovered this - and perhaps his wife was going to leave him and take the child (like the 2009 family). Molly 'disappeared' in the night i.e. became Vincent again and was taken away somewhere to be abused by Ian. His wife suspected Ian was involved but had no proof.
Ian had a hold over Vincent - he would hurt Vincent's mum if Vincent talked - Ian's wife and Vincent's mum being the same person. However, Vincent had been brought up by someone else (Sylvie?) and thought of her as his mother.
When Vincent visited Ian's wife in the nursing home, he had not seen her since he was a young child, and didn't remember his early life as Molly, so related to her as he would a stranger. She did not recognise him because her mind has completely gone by 2014.
Oh, and Vincent is not reacting to his medication. Malik slipped a slow acting poison into his drink once he got the information from him. Far fetched? 