"Rob seems really happy with Blac Chyna. He's really not thinking about what his family thinks, or how everyone else feels," the source tells PEOPLE. "He's had a really hard couple of years and so if she makes him feel good, that's all that matters right now."
Blac Chyna has a complicated relationship with the family, and a source previously told PEOPLE Rob's sister Kylie Jenner is "livid" about the relationship. Blac Chyna, 27, was once close friends with Rob's sister Kim Kardashian West, but that friendship soured when Blac Chyna's ex-fiancé Tyga began dating Kylie. Tyga and Blac Chyna share one son – King Cairo, 3.
But those familial complications have not lessened Rob's enthusiasm for the romance.
"It's no secret that Rob has had tension with his sisters over the years," says the source.
Kardashian, 28, has been out of the spotlight for the past two years as he struggled with depression, significant weight gain and a health scare that saw him hospitalized and diagnosed with diabetes.
A source previously told PEOPLE that Rob will no longer be welcomed back at sister Khloé Kardashian's home, where he has been living.
"Rob has been lonely for so long, so of course it's great for him to spend time with someone other than his sisters," the source previously told PEOPLE. "Rob has also found an escape from his family nagging him about his heath. He has ignored their attempts to contact him."