Lindsay Shookus - who previously dated the 'Batman v Superman: Dawn of Justice' star, who has since moved on with Alex's ex Jennifer Lopez - was seen hanging out with the television producer over the weekend as he helped to celebrate her birthday.
A source told The Sun newspaper's Bizarre column: "It’s certainly going to raise eyebrows, given Ben and Jennifer are back together so publicly. What are the chances that both of their exes have now hooked up? It's started a lot of whispering on the rumour mill."
A video clip of the party shows Lindsay and Alex sitting alongside each other at the intimate party in the Hamptons, whilst magician Josh Beckerman impressed guests with his skills.
However, a representative for the baseball star has insisted there is nothing happening.
They said: "There is absolutely zero there. They’ve been friends for 15 years."
It comes after a source revealed Ben and Jennifer are "inseparable" at the moment.
An insider said: "They are inseparable and it's going really well, Jennifer has never been happier and knows it was meant to be ... Her kids really like Ben and think he's funny and fun to be around. He's totally won the family over with his charm. Ben was very good with them. He was asking them questions and smiling. He was very engaged and seemed to like hanging out with them."
The family all went out together for a dinner out and Jennifer's mother Guadalupe has continued to develop a good relationship with Ben and is "thrilled that they are back together now".
A source said: "In the past, Jennifer's mom and Ben were very close. Guadalupe loved Ben. She was sad when they couldn't work things out years ago. She is thrilled that they are back together now."
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