It is not clear from your question as to the nature of the videos of you and your boyfriend. There is no prohibition against videotaping people or property that are open to public view. However, assuming that is not your scenario, there are numerous provisions in the Canadian Criminal Code that might cover your situation.
First of all, since you mention the threat by your Ex in-laws to reveal the videos to others, we presume they would fit the Criminal Code definition of “intimate image”, defined in s. 162.1(2) to include a visual recording in which a person is “nude, is exposing his or her genital or anal region or her breasts or is engaged in explicit sexual activity”. This definition also requires that the recording was made when you and your boyfriend had a reasonable expectation of privacy, and that you continued to have a reasonable privacy expectation afterwards. Section 162.1(1) of the Criminal Code makes it an offence when someone “publishes, distributes, transmits, sells, makes available or advertises an intimate image” of a person without the consent of that person. The maximum penalty is five years imprisonment.
Section 162 of the Criminal Code also establishes laws against voyeurism, and publishing images that derive from that. It is also an offence under s. 184 of the Criminal Code to “knowingly intercept” (which includes “record”) a private audio communication by means of any mechanical or acoustic device, unless one of the people in that private conversation gives consent. This exception does not seem to pertain to your situation, meaning that if you Ex in-laws recorded private communication without your or your boyfriend’s consent, this would be an offence also.