After my wife was diagnosed with breast cancer, I was a clueless husband and an equally clueless dad. I didn't know how best to support my wife (eventually I figured out my job was to shut up and listen to her.) As for our two teenage daughters, they seemed to be doing okay. So while my wife and I made sure to keep them up to date on the medical news, I never asked a simple question: How are you doing?My wife and I just thought: They're still acting like typical teens: stressed by schoolwork, eager to hang out with friends, perpetually annoyed at their parents. They must be okay.Now my older daughter Maya and I have written a book for teens coping with a parent's cancer. I've learned a lot about how tough it is for these teens – ready to pull apart from the family and form their own identity, then yanked back into the fold by cancer. Here's what I wish we'd said to our dear teenage daughters:1. If you have questions, ask them. We can meet once a week, we can put a notebook in the den for you to jot questions in – and we'll answer them. And if we seem too busy with cancer appointments and such, ask Mom's sisters. Either they'll have the answer, or they'll find out.2. We will probably need your help. Since mom is dealing with treatments and I am her appointment companion, we definitely have less time to keep up household stuff. Sometimes we might ask for help. Sometimes we might forget to ask. If you can offer – I'll do the laundry, run the dishwasher, empty the cat's litter box – we'd be incredibly grateful. 3. You're not doomed to develop breast cancer. Only 1 in 10 cases of breast cancer are due to the inherited genes. So mom's breast cancer doesn't mean you are destined to develop the disease at some point. On the other hand, one in eight women are diagnosed with breast cancer, so you are at risk. And I know this sounds like "a boring lecture from Dad," but healthy living is one way to reduce the risk. Studies have shown that three alcoholic drinks a week raise your risk 15 percent compared to nondrinkers. Smoking and being overweight also up the risk, while four to seven hours of moderate to intense exercise a week will lower your risk. 4. It's okay to be mad at us. Mom may have cancer and chemo may make her feel like crap. But we don't expect you to become perfect angels. "It's a fantasy that people who love each other don't get mad at each other," says psychiatrist Paula Rauch, who runs the Marjorie E. Korff PACT Program (Parenting At a Challenging Time), which provides support for families when a parent has cancer. "In fact, you get mad at people you love because you expect a lot from them." I heard of one newly diagnosed mom whose daughter said, "Now I can't even get mad at you." The mom replied: "You can still get mad at me. Even though I'm going through a hard time, I'm still able to manage that you get mad at me. I'm sturdy enough. It might be hard for me, but I'm still your mom."5. Let's still have family fun. Cancer may seem to be running our lives for the next few months: doctor's visits, chemo sessions, post-chemo recovery days. But let's grab some fun time anyway. You pick the activity: movie, ice-skating, a hike, a pizza outing. And let's just do it. Hey cancer, you can't be the boss of us!Marc Silver is the co-author of My Parent Has Cancer and It Really Sucks (parenthascancer.com) and the author of Breast Cancer Husband (breastcancerhusband.com).