The 26-year-old rapper - whose money problems have dominated the internet for the past few months - has been dating the 19-year-old businesswoman on and off for over a year but her famous family, including her mother Kris Jenner and sister Kendall, are said to be worried he's using her for cash.
A source explained to Grazia magazine: "The family are increasingly worried that Tyga isn't good news. They worry he's a hanger-on after learning he owes a lot of people money, and has borrowed thousands of dollars from Kylie. She's not the most worldly of sisters and they'd hate to see her taken advantage of."
The couple have even started talking about marriage in recently months and Kris - who also has daughters Kim Kardashian West, Kourtney Kardashian and Khloe Kardashian and son Rob Kardashian - is terrified Kylie will run off to tie the knot without securing her finances with a prenup.
The insider explained: "The couple have even talked marriage and Kris' biggest panic is that Kylie might do something stupid, like elope without a prenup. She's asked Kendall to keep an eye on Kylie and discourage her from doing anything rash."
Meanwhile, Kylie's family certainly have a reason to be worried as it is believed Tyga has had two of his cars repossessed in the past six months and reportedly owes his former landlord money after he failed to keep up with his monthly payments.
Four months ago, it was revealed Choice Motor Credit (CMC) were trying to take back his 2013 Lamborghini Aventador as he owed them $357,350.77 for not making payments.
And CMC also repossessed his 2014 Bentley Mulsanne in February.
Though the firm sold the car, Tyga still owed them over $91,000 several months later.
Last month, the 'Ayo' hitmaker's former landlord,F&S Investment Properties, claimed he owed them $186,275 after he rented retail space for his Egypt Last Kings Clothing and allegedly trashed it.
He also allegedly owed Gholamreza Rezai $480,285.00 in damages for his old rental home, which he vacated "sometime prior to" October 31, 2012, but has now settled the case after making a confidential agreement with the owner of his old home.