I had the same issue in 1.6 beta. I opted out of the beta and re-converted my xbox edition world today to the bedrock version. I had 2 baby villagers in the converted world that grew up and disappeared on their own. 2 other villagers locked in a house refuse to breed. They have no troubles breeding in the xbox one version of the game.

Update: It appears that letting the villagers out of the locked house triggered them to start breeding.. 3 villagers within 5 minutes