Lapointe was hired in 2010 after Boisvenu was named to the Senate by Prime Minister Stephen Harper.
The news of the investigation came in a letter to Liberal Senator Céline Hervieux-Payette, who complained about the situation in June after media reports alleged a romantic relationship between Boisvenu and Lapointe.
"I was pleased that she accepted to do it," Hervieux-Payette said from Montreal this afternoon.
Hervieux-Payette said the ethics officer agreed that an investigation is justified according to Articles 8 and 9 of the Conflict of Interest Code for Senators.
The code says senators may not act in any way to further their private interests, or those of their family members, when performing parliamentary duties. It also says senators may not use their position to influence a decision of another person in order to further their own private interests, or those of their family members.
Hervieux-Payette said Boisvenu only decided to let go of Lapointe when it became public that they were involved at the same time that she was working in his office.
"He did not respect the code of ethics that applies to all of us," Hervieux-Payette said.
According to Hervieux-Payette, Lapointe went on to work for the Senate's administration. Hervieux-Payette has asked the ethics officer to determine what the consequences are for seeking favoured treatment for a family member.
"It's stupid to put the integrity of an institution on the line with people who aren't ethical," she said.
Lapointe now works for Conservative Senator Don Meredith.