It was a difficult nine months for Rob Kardashian and Blac Chyna, and more than once the new dad's sisters found themselves in the middle of the drama.

In a promo for Sunday's season finale of Keeping Up With the Kardashians, which was taped before Rob and Chyna's daughter, Dream, was born, Kim Kardashian West shares with sisters Khloe and Kourtney that the engaged couple are "fighting again."

WATCH: Blac Chyna Reveals She Lost 15 Pounds One Week After Giving Birth -- See Her New Weight

When Khloe asks what the argument is about this time, Kim explains, "I don't know. I mean, she texts him crazy things, he texts her crazy things all night long."

She then reveals that their 29-year-old brother does not want to attend the baby shower they have been planning for him. "He doesn't want to celebrate a shower because this pregnancy has been really bad for him and really awful for him," Kim says.

WATCH: Rob Kardashian Practices Daddy Duties With the Help of Scott Disick

The sisters then decide to step in and see what they can do to get Rob to the party. "You guys, our brother is coming to the shower. That's crazy," Khloe exclaims. "We should try to get him to come for Mom. If it's for nobody else, it should be for her. She does so much for him."

"We just really wanna do this for Rob, especially my mom," Kourtney reiterates about their mother, Kris Jenner. "She's so excited to give him presents and just, like, really celebrate him. So, I think she's definitely not going to take it well if he doesn't show up."

WATCH: Kris Jenner Shares Super Sweet Photo of Ecstatic Rob Kardashian Holding Baby Dream

While Rob and Chyna had their share of arguments leading up to the birth of their daughter, a source tells ET that the two are "doing well" since Dream came into their lives. "All is good with their relationship right now," the source says, adding that Rob and Chyna are "doing a great job at co-parenting and staying under one roof."