Whitney Houston's brother and sister-in-law arrived in Los Angeles yesterday to attend Clive Davis' big pre-Grammy bash ... a bash Whitney's mom called "obscene."

Whitney's mother Cissy slammed Davis' invite, saying, "I got an invitation to the party, which is the most obscene thing. I don't know why they would want me to come to the party in which she died, you know? I guess maybe he just sent me a copy for remembrance sake."

Whitney's brother Gary -- along with his wife Pat (who was also Houston's manager) -- begged to differ and flew into LAX Saturday, telling us they were going to "support Clive."

Houston was found dead in her hotel room this time last year, just hours before Davis' annual party just floors below.

Bobbi Kristina is on a mission to make sure grandma Cissy Houston's new tell-all book crashes and burns -- by BOYCOTTING it altogether and pleading with her fans to do the same.

Cissy released a book this week called "Remembering Whitney" -- which is all about Whitney Houston's life -- and made the rounds on a slew the talk shows promoting the hell out of it.

But Bobbi wasn't too happy, tweeting to her 119,000 plus followers, "Anything concerning my grandmother's book, I and @nickgordon of course personally have nothing to with."

She continues, "I haven't read and won't ... I find it to be disrespectful to my mother and me being her daughter won't tolerate it."

FYI -- Cissy was on Oprah earlier this week (again promoting the book) and admitted her relationship with BK was strained ... and admitted she knew that Bobbi didn't want the book written.

Bobbi Kristina's grandmother Cissy Houston has BACKED OFF her attempt to keep Whitney Houston's money from Bobbi Kristina for years -- we found out Cissy has settled her beef with BK.

TMZ broke the story ... Cissy and Pat Houston (co-executors of Whitney's estate) ... had filed legal papers hoping to drastically change the way Whitney's fortune would be paid out to 19-year-old Bobbi .. because they felt it was "too much, too soon."

As it stood, BK was to receive her money -- an estimated $20 million -- in 3 separate chunks ... 10% when she turns 21 ($2 mil), just under 20% at age 25 ($4 mil) and the remainder when she turns 30 ($16 mil).

Now, we've learned ... the case has been dismissed after Bobbi and Cissy reached an agreement ... and sources tell us Whitney's original plan for the payout was virtually unchanged.

Still, we're told both Bobbi and Cissy are satisfied with the plan ... and are happy to put the case behind them.

Whitney Houston's mother Cissy is deathly afraid Bobbi Kristina will die just like the singer -- in a haze of drugs and other bad influences -- which is why she wants to withhold Bobbi's multi-million-dollar inheritance, sources tell TMZ.

Sources close to Cissy tell us, Cissy feels Bobbi is currently surrounded by numerous negative influences -- including her boyfriend Nick Gordon and father Bobby Brown -- who will drain Bobbi's fortune given half the chance.

We're told Cissy also feels 19-year-old Bobbi is still extremely impressionable right now -- and if left unchecked with millions of dollars, Bobbi could end up going off the rails ... eventually dying just like Whitney.

According to sources, Cissy wants to wait until Bobbi has matured significantly more before she gets her money ... an estate estimated at $20 million ... though it's unclear how long she wants her to wait.

As for allegations Cissy is trying to withhold Bobbi's fortune to hoard the money for herself -- Cissy is telling friends that's total BS ... that it's about protecting her family.

As we reported, Cissy and Whitney's sister-in-law Pat Houston filed a request this week to modify Whitney's will -- in order to change the distribution schedule of the estate.

Whitney Houston's family wants to put the singer's fortune on lockdown to stop Bobbi Kristina from blowing her inheritance ... and to protect BK from financial leeches.

Cissy Houston and Pat Houston, Whitney's mom and sister-in-law, filed a request this week to modify Whitney's will. Specifically, they want to change the distribution schedule of the estate ... estimated to be worth at least $20 million.

Sources close to the family tell TMZ ... Cissy and Pat filed the documents because they think the current will gives BK "too much too soon" -- and they don't think she has any need for that kinda cash now.

We're told the family also wants to "protect [Bobbi Kristina] from herself" ... because she's vulnerable. In the documents, they claim 19-year-old Bobbi "is a highly visible target for those who would exert undue influence over her inheritance."

Bobbi Kristina, Whitney's sole heir, is currently scheduled to get her inheritance in three chunks -- 10% when she turns 21, just under 20% at age 25 ... and the balance when she's 30.

In their petition, Pat and Cissy don't mention what specific changes they are seeking to the current payment schedule -- but they say Whitney's intent was "to provide long-tern financial security and protection" for her daughter.

Cissy Houston was not happy this weekend when she was booked at the same hotel where her daughter Whitney Houston died ... but she does want to visit her daughter's death room at some point ... TMZ has learned. 

Whitney's mother is in Los Angeles this weekend for the BET Awards (where Whitney will be honored) and we're told she felt uncomfortable when she was set up at the Beverly Hilton -- the same hotel Whitney passed away in back in February.

Our sources say Cissy does want to visit room 434 for closure and is planning to contact the hotel this weekend ... but that she wants to do it on her own time.

According to our sources, Cissy's reservation was moved to the Regent Beverly Wilshire instead.

Whitney Houston's mom is pulling a Joe Jackson -- cashing in on her child's tragic death ... that's what some family members think of Cissy Houston's plans to write a tell-all book.

Sources close to the Houston family tell TMZ ... Cissy's new publishing deal with Harper-Collins for a memoir is merely a lame attempt to make money -- since Whitney left everything to Bobbi Kristina -- and not at all about honoring the late singer.

One source said the book -- which is slated for release next year -- could also be a PR move for Cissy, claiming ... "She will try to come out looking like the world's greatest mom, when in actuality, she wasn't."

Whitney Houston's mother is telling friends ... she fully supports the idea of a family reality show because she believes the exposure will be GREAT for Bobbi Kristina's singing career.

As we previously reported, the family just inked a TV deal with Lifetime to star in a reality show that will follow Whitney's relatives in the wake of the singer's untimely death.

Houston family sources tell TMZ ... Cissy Houston knows BK shares Whitney's passion for music ... and she believes a reality show could be the perfect place to showcase Bobbi's talent.

We're told ... Cissy also believes a reality show will "help with the healing process" by "keeping the family as one."

Cissy also likes the fact that her "extended family" will be making money from the deal.

But don't expect Kardashian-style antics on the Houston show -- producers are suggesting it will have a more serious tone ... at least for now.

Whitney Houston's daughter Bobbi Kristina -- and several of her relatives -- have signed a deal to star in a reality show for Lifetime called "The Houston Family Chronicles."

The show will focus on Pat Houston, Whitney’s sister-in-law and manager, Pat’s daughter Rayah, Whitney’s brother Gary, and Whitney's mother Cissy. 

Lifetime's EVP, Rob Sharenow says, "In this series, the multi-generations of the Houston family will bravely reveal their lives as they bond together to heal, love, and grow."

So we gotta ask ...

Whitney Houston's mother is "devastated" and "inconsolable" over the L.A. County Coroner's Autopsy Report that makes it clear ... Whitney was deep into cocaine when she died.

Cissy Houston is telling close friends ... she cried hysterically when she first heard about the Coroner's findings -- that white powder (which we know tested positive for cocaine), a drug spoon and other trappings of drug use were found in the hotel room. 

Cissy says her biggest fear is that people will now remember her daughter as a druggie, and not a talented singer and family woman.

Cissy singled out Whitney's performance of the National Anthem at the 1991 Super Bowl, saying, "This is the type of thing people should remember Whitney for."

Cissy added, "No one's perfect. Only the Lord can judge."

Whitney Houston's mother believes Bobby Brown's DUI arrest proves what she's been telling people all along ... he's just a bad dude.

Sources close to Cissy Houston tell us ... she's always felt Bobby was a cancer ... who infected Whitney's life with negative influences.

We're told Cissy felt "vindicated" when she found out Bobby was arrested for driving drunk on Monday afternoon ... and believes the incident is exactly why she wants Bobby to "keep his distance" from his daughter Bobbi Kristina.

The Houstons believe Bobbi K has been in a "vulnerable place" since Whitney passed ... and as one source puts it, "This is the last person she needs to be around."

Instead, we're told Cissy wants Bobbi Kristina to hang around "positive mentors" ... like Clive Davis.