Amanda Bynes is Engaged But Family Won't Approve Marriage

Amanda Bynes' engagement ring is an Amazon bargain ... and her family is going to block her from tying the knot.

Sources close to the family tell TMZ ... Amanda will never legally marry her fiancee, Paul Michael, because her mother holds the keys to marriage and she doesn't approve of her daughter's engagement.

Amanda's mother is her conservator, and we're told Amanda cannot get married without her conservator's consent. Our sources say the family feels it's not in her best interest to be married -- they haven't met Paul -- so a wedding ain't happening.

As for the engagement ring ... our sources say Paul bought it off Amazon for $49, and Amanda is telling those around her the ring is NOT a real diamond and she's fine with a fake.

As you know ... Amanda met Paul in AA and they've only been dating for a few months. She introduced him to her fans on social media by calling him "drop-dead gorgeous" and the "best person on the face of the Earth." She also says they've both been sober for over a year.

Our sources say her family believes Paul doesn't have a job. Amanda had a boyfriend right before him, and we're told her family thinks he might be a rebound.