Chad Ochocinco was confronted by his ex's mother -- who demanded the NFL star pony up the $38k in child support he owes her daughter ... but Chad says the amount is just not fair.
Here's the backstory ... Chad was leaving his son's middle school graduation in California last month, when he was confronted by the grandmother of one of his other children and some of her friends.
The woman was trying to serve Chad with court documents -- in which he's accused of stiffing the mother of his 14-year-old son out of $38k in back child support.