Rapper Big Sean has been leaning on his girlfriend Ariana Grande following the death of his grandmother.

According to a source, Sean, 26, has been left devastated following the loss of his grandmother Mildred Leonard, who passed away Dec 19 at the age of 93.

Now, Grande, 21, is said to be doing a great job comforting him, reports hollywoodlife.com.

`Ariana has never seen Sean so emotional in her life and she's comforting him as best as she can. His grandmother was such a driving force in his life,` the source said.

`It's a somber moment for Sean, but it's actually bringing him and Ariana much closer together. He's leaning on her and she's as strong as a rock. This time is completely difficult for Sean and he'd be lost without Ariana,` the source added.

Sean took to his Instagram account Dec 23 to post a picture of his grandmother and attached a heartfelt tribute to her in which he admitted he was having a `hard time` accepting her passing and thanked her for making a `better life` for his family.

`My grandma passed away a couple days ago. I haven't said anything to anyone because honestly I feel like she's still here. I definitely can feel her consciousness.

"I'm having a hard time accepting her death, but I must acknowledge my grandma's life, a true hero... She made a better life for me and the rest of my family, and I will forever be grateful I got to know and be loved by such an amazing woman! I'm so proud of her...` he wrote.

Sean had confirmed his relationship with Grande in October.