My 14 year old son crossed ually appropriate boundaries with my 12 year old step daughter. Advice needed?

My wife & I married 7 years ago, each bringing 2 children into this 2nd marriage My two sons have been a major cause of heartache throughout the marriage 6 years ago my then 12 year old son inappropriately touched my then 6 year old stepdaughter My wife & I shocked went through all appropriate legal channels etc & somehow moved on I removed that son out of our home within a year due to other behaviors etc We continued to try & help him for the next 4 years to no real avail My wife & I will take all those memories to our graves My younger son 14 has adhd and has had behavioral problems all his life, primarily impulsive It has also taken it's toll yet somehow we have managed & actually gotten to the strongest point in our marriage. Her children have gone completely according to plan and have thrived in this blended family 3 weeks ago my youngest entered my stepdaughters room pulled her covers up and tugged at her pajamas Wife has withdrawn, trying to save all Help.