Donald Trump Jr. reportedly pulled out of a fundraiser event with Jeb Bush’s son, George P. Bush, after the ex-presidential candidate and his family continued to attack the president via Twitter. Axios reported Thursday that Don Jr. and George had formed an “unlikely alliance” despite their fathers’ mutual loathing, and that Don Jr. was planning to headline at George’s campaign fundraiser on June 25th. The pair’s relationship grew strained, Axios reports, as Jeb Bush attacked the president on Twitter—and the “final straw” came Wednesday, when Bush tweeted that “Children shouldn’t be used as a negotiating tool. @realDonaldTrump should end this heartless policy and Congress should get an immigration deal done that provides for asylum reform, border security and a path to citizenship for Dreamers.” The sources report that Don Jr.’s cancellation isn’t personal, and is instead “collateral damage” in the bitter feud between their fathers. George P. is running for re-election as Texas land commissioner.