John Fletcher is a black hole for Oxfordian theorists. Too close and the whole Oxfordian shebang disappears in a wail of deplorable sucking noises. It's a good job his early life isn't as well documented as Shakespeare's or there wouldn't be any Oxfordian case at all.
He's a bit of a man of mystery until his 27th birthday in 1607 which was shortly followed by the appearance of The Woman Hater, co-written with Francis Beaumont. The two dramatists became a team and wrote many of the most successful plays of the decade following Shakespeare's retirement. The fact that Oxford was dead and gone before Fletcher appears on the scene is a fatal embarrassment to the idea that the plays were complete before 1604.