Now Matthew Broderick has responded to his request, telling US Weekly that "of course" Robert could reach out to Sarah Jessica.
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Matthew Broderick and his wife Sarah Jessica Parker
Speaking at the opening of his Broadway show, It's Only A Play, Matthew, 52, said: "Of course, he's more than (okay to connect with her) – they're great friends.
"What would I say? No? Who do you think I am? No, I love Robert Downey and Sarah Jessica, so (yes!)."
Sex and the City star Sarah Jessica is also on board, adding, "He and I have always been on wonderful terms, so… of course I'm hospitable to that!"
Sarah Jessica Parker and Robert Downey Jr dated for seven years in the Eighties
Robert and Sarah Jessica, both 49, started dating when they were 18 after meeting on the set of Firstborn in 1984. They were together for seven years before splitting because of Robert's troubles with drug and alcohol abuse.
Sarah Jessica has been married to Matthew for the past 17 years. Robert, meanwhile, is expecting another baby with his wife Susan Downey.
It was last week that Robert told radio DJ Howard Stern he would like a reunion with his ex while he is visiting Manhattan.
Robert Downey Jr is expecting another child with wife Susan Downey
"I'll make a point of trying to see her while I'm here. I'd like to," the Iron Man star said. "I'll ask (Matthew's) permission. I just want to check in for a few minutes. I love Matthew Broderick."