Senate Judiciary Committee Chairman Chuck Grassley (R-IA) declined to rule out Tuesday that his panel may launch an investigation into President Donald Trump’s son for having parts of his wedding funded by a Russian oligarch with ties to Russian President Vladimir Putin.

The revelation came in response to an unusual written request from a fellow Republican, Sen. John Curtis (R-UT), that the committee dig into “the use of presidential family relationships for private financial benefit, preferential treatment, or access by domestic and foreign interests.”