Mary Bryarly was I believe his first wife, at least this is what other family histories record.
His second marriage took place 27 Jan 1785 in Frederick Co. VA to Ann Peters. You should be able to get a copy of their original marriage bond through L.D.S. library system on film or if you live in VA through the State of VA inter-library loan system.
You might be able to find land deeds which can narrow down the time period of each marriage.