Washington (CNN) Donald Trump Jr. has withdrawn from a fundraiser for George P. Bush in New York because of criticism stemming from the Bush family -- notably Jeb Bush -- a source with knowledge of events confirms to CNN.

Trump Jr. personally likes George P. Bush, the source said, but cautioned him in recent weeks that he would not be able to publicly support him if Jeb Bush -- a 2016 rival of Donald Trump -- continued to criticize the President.

"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," Jeb Bush, George P. Bush's father, tweeted Monday.

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. https://t.co/OOjv0vNeVg — Jeb Bush (@JebBush) June 18, 2018

The tweet was the last straw for Trump Jr., the source told CNN. His withdrawal was not related to a similarly critical Washington Post op-ed by former first lady Laura Bush , this person added.

The fundraiser was scheduled for New York on June 25.