Predictive testing for Huntington disease (HD) in 25% at-risk individuals is testing with full knowledge, and sometimes assuming, that the parent does not want to know his status. The goal of this study was to understand: (1) the differences in the motivation between 25% and 50% at-risk individuals to be tested and (2) the consequences of “double disclosure”, including parental reactions. Test requests from 25% at-risk individuals were rare (155/1611, 10%). We compared their motivation with those of 1456 50% at-risk individuals. The principal motivation to have the test for both groups was “to know” (48% versus 58%, p = 0.049), but the desire to have children was more frequent in the 25% at-risk group (32% versus 17%, p < 0.001). Sixty percent of the 25% at-risk group went through the testing procedure: 15% (n = 14) were variant positive for HD. Testees reported four adverse reactions of their parent (22%): one committed suicide and three became depressed. This result highlights the impact of “double disclosure”, a bad result for the person themselves and the transmitting parent. It is the responsibility of the team to anticipate this outcome with the 25% at-risk individuals: children revealing the genetic status to their parent. They should help the testees and their family to find a satisfactory solution to help prevent adverse reactions. This includes ensuring that the candidate is well-infomed abour the testing options and consequences to her/himself but also to her/his parent. The at-risk parent should be offered to discuss the implications of their child’s testing.