Blac Chyna didn't have Tyga's phone number until they started planning their son's birthday party.
The former couple were spotted in the same company last weekend for their boy King Cairo's fifth birthday at the Six Flags Magic Mountain theme park in California, which they are said to have spent two months planning with the help of the youngster's nanny.
According to gossip website TMZ, the pair are now willing to put their differences aside in public for the sake of their son, partly thanks to Cairo's babysitter acting as a peacemaker in the party negotiations.
They are said to have decided to try to get along more for the sake of their son and because him starting kindergarten will mean they will need to chat about his schooling on a regular basis.
In March, Chyna appeared to slam Tyga - whose real name is Michael Stevenson - for not paying child support for their son, launching a furious tirade on Snapchat.
She posted: "It's funny now to me!!! But when Tyga and side n***a kicked me out!!! And they wanted to see me fail! lol And 2 grind from the dirt!!!!!! No child support! N***a is like hoes!
"So imma treat u like that! Not paying Jenny ! Wow. Stop running to ur money! Telling my business about King!
"I bet any money ! I got more money then ur account Tyga, Michael !!!
"So go tell Kylie [Jenner] and Rob [Kardashian]! About our son Account! Cause that's the only reason I'm contacting your f**a**!
"But u wanna make it like I want u lol! Tyga ur a b****!
"And u can go get ur mom, or ur b****! Lol!!! Or ur n***a u f***in or Terrell or heather! (sic)"
At the time, Tyga was dating Kylie Jenner, the half-sister of Rob Kardashian, who Chyna has 11-month-old daughter Dream with.