This family row may be a blessing in disguise, because dear Gurms, you seem to be sleepwalking to disaster.
My thoughts are based on assumptions, so they may be wrong.
I am assuming that your elder son lived in the family home, and continued living there after he married and when your husband died. You continued supporting him and his wife despite them both earning well and cannily investing their money elsewhere. Your younger son lives in Toronto, my assumption is that he left home but was furious that his brother was taking over his old room, thus leaving him nowhere to stay if he returned.
All three of them are behaving appallingly by virtually estranging you, in your own home, particularly the married pair who are benefiting financially; your son has no right to continue living in your home because it was once his father's. I suspect when your husband died you were glad he/they were there, but he has taken a gross advantage of the situation.
Next they will be suggesting you surrender your rooms because theirs are too small until eventually you will be forced out of your home. (There are echoes of a book I once read about this happening to a woman but I can't remember the details.)
You need to clarify the situation with a lawyer and either register son and wife as lodgers with a legal agreement for payment, or more sensibly, get them out, although I suspect that will be difficult. Under no circumstances allow them to touch any other rooms for their new baby.
This is a horrible situation for you when you should be able to look to your sons for support, and spoiling your anticipation of a grandchild, but I fear if you do not take action now it will only get worse, financially and emotionally.
Your counsellor, by the way, does not sound to be of much use,