Will children services take your child away if they find out your boyfriend was convicted of involuntary manslaughter but has served his time and is off parole?

Answer 1

Actually, Social Services only has jurisdiction if, and only if, a new complaint of abuse or neglect is made. They may investigate only that allegation. They may review past convictions, but since those past convictions rarely have anything to do with new allegation, cannot use this to make determinations regarding minor children.
The fact that a person has been previously convicted is not an indication or determination of "risky behavior" on the part of anyone, especially in the US. Consider for a moment that there are 350 million Americans. Currently there are 2.5 million people incarcerated (these are felony convictions), and this is fully 25% of the total incarcerated population of the world (while the US represents only 5% of the world's population). That 2.5 million represents about 25% of the total number of previously incarcerated Americans, meaning roughly 10 million or so Americans have felony convictions, 1/35th of the US, and this number is rising daily.
The child or children must come under the jurisdiction of a court for the child or children to be removed, and this cannot happen unless the child has been abandoned, abused, or neglected in some way by the previously convicted person or parent, or if the conviction of that person was for some manner of abandonment, abuse, or neglect of the child's or children's siblings.

Check the laws of your state. And, if Child Services does come after you, do what you must to protect your children, but do everything you can to make Child Services pay for everything wrong they do.