Sounds like your MIL is going to have both of her sons back under her roof, i.e., one big happy family reunion. It will be very interesting in that household if they both are back home.
What kind of puppy did you get? I'm sure that all of you will enjoy the little fur baby and yes, it takes a lot of time and patience to train a new puppy. Be sure to put your shoes in the closet as they do love to chew!
Sit quietly, the answers will reveal themselves when you least expect them to. The past is gone, the present is a gift and you need to focus on today, allow the future to reveal itself when it is ready.