Jennifer Hudson's half-brother is in jail this morning after being accused of stabbing a man in the face!

The man was allegedly involved in a relationship with his estranged wife.

Hudson's half brother, Steven Simpson, is now in custody in Paw Paw, Michigan, and he's expected to be charged with home invasion and attempted murder.

FLASHBACK: The ex-boyfriend of Hudson's sister murdered her mom, brother and nephew in a jealous rage.

Source: TMZ