Whitney Houston's Family -- Nick's Not Welcome Here ... For ONE FULL YEAR

Whitney Houston's sister-in-law just got a year's worth of peace of mind ... a judge has just ordered Whitney's son-in-law Nick Gordon to stay clear of her for the next year.

We broke the story ... Pat Houston got a restraining order against Nick last month ... claiming he made threatening comments against her and posted ominous photos of guns on Twitter.

Now a judge has extended the order for 12 months, so Nick can't contact Pat or anyone in her immediate family ... he comes within 200 yards -- he goes to jail.

The bad blood is long-standing. Family members tell us Nick resents Pat because she controls the purse strings of Whitney's estate ... and he thinks his wife Bobbi Kristina got screwed on her inheritance.