IT consultant Nima Momeni fatally stabbed CashApp founder Bob Lee through the heart after the pair fought about the suspect’s sister — and whether they were doing “anything inappropriate,” new court documents released Friday allege.

Police claim that before Lee was murdered on the streets of San Francisco in the early hours of April 4, Momeni and the slain tech entrepreneur had talked on the phone about his sister, Khazar Elyassnia, who was married to someone else.

An unnamed witness told police that Momeni grilled Lee about his sister, asking if Elyassnia, who is married to a prominent plastic surgeon, was “doing drugs or anything inappropriate.” 

Lee, 43, assured his alleged murderer that nothing out of bounds had happened.

Police didn’t elaborate on the relationship Lee had with Elyassnia, who was not named in the court documents.

The witness told police it was unclear to them if Lee and Elyassnia had an “intimate relationship.” 

Lee had been estranged from his wife, with whom he shared two young girls, at the time of his murder and had moved from California to Florida with his dad.

That fateful night, Momeni drove Lee to a “dark and secluded area” of San Francisco, the charging documents allege, where he stabbed him through the heart with a kitchen knife.

Momeni brought the knife with him from his home, which police said makes clear the murder was “planned and deliberate.”

Khazar texted Lee around the time of his murder to check in on him, the documents claim.

“Just wanted to make sure your doing ok Cause I know nima came wayyyyyy down hard on you,” she wrote.

“And thank you for being such a class man handling it with class. Love you Selfish pricks.”

Momeni was arrested Thursday morning after an exhaustive investigation and made his first appearance in court Friday, which attended by his sister and her husband. He flashed a heart sign to her from the dock and she responded with the same symbol. Momeni is set to be formally arraigned on April 25 and faces more than 20 years in prison if convicted.