askable parent
n. A parent who is willing to answer their child's questions and who encourages their child to ask questions, particularly about sex.
Mary Ann Roll, a longtime PTA leader who was instrumental in bringing Can We Talk? to Rhode Island, says: "If I could do that part of my own kids' life over again, I would do it differently. For one thing, I'd … talk with them more. I don't think I was an 'askable' parent. I could have used help."
—Julia Steiny, “Learning to talk about sex with kids,” The Providence Journal (Rhode Island), April 25, 2004
Regardless of your position, one principle should guide every parent - start talking to your children about sex, soon and often. So says every expert in the field, from educational psychologists to crisis pregnancy counsellors.

Don't wait until they are teenagers for one big conversation - have endless little conversations that begin when they start asking questions.

Children really need to know that there is nothing wrong with asking their parents questions about sexuality. This is why the American Social Health Association coined the term "askable parents". Children who learn about sex from "askable parents" learn values and love along with the facts.
—Louise Holden, “Talk to your children about sex now and keep talking — otherwise it could be too late,” The Irish Times, May 20, 2003
1981 (earliest)
A fee of $15 will be charged for the New Rochelle program, which focuses on ''Preparing Parents for Their Roles as Sex Educators.'' In White Plains, the fee is $20 plus $3 for materials, and the subject is ''Talking to Your Children About Sex: Are You an Askable Parent?''
—Eleanor Charles, “Westchester Guide,” The New York Times, January 11, 1981