Adding weight to the claims, French, 29, appeared in a number of photographs taken at Kendall Jenner's intimate 19th birthday celebrations on Monday.
Khloé Kardashian and French Montana are said to have rekindled their romance
In a new Instagram post, Kendall shared a number of polaroids taken on her big day, and can been seen posing with friends, her mum Kris Jenner – and her sister Khloé's ex-boyfriend.
French also shared a picture from the party on his Instagram page, showing him cuddling up to the birthday girl and mum Kris.
A source told Hollywood Life that Khloé decided to give the rapper another chance "after weeks of him proving how serious he was about her".
French Montana appeared in a number of photos taken at Kendall Jenner's birthday party
It's perhaps not surprising that the couple have reconciled; both Khloé and French have been very vocal about their close connection, even after splitting up.
"We all miss French. We love French," Khloé, 30, told E! News earlier this month. "I'm still friends with him. I still talk to him every day."
French, meanwhile, told US Weekly: "She's my baby forever. She's good. She's the best. There's no bad blood with her.
The rapper shared this photo taken with Kendall and Kris Jenner
"I love how she is. She inspires me as a person. I'm sure I inspire her in many different way. We just have that special relationship. Right now we're in a special zone… She's a beautiful person. I don't think a lot of people know how beautiful she is."