Family history is a risk factor for asthma, with many different genes being implicated.  If one identical twin is affected, the probability of the other having the disease is approximately 25%.  By the end of 2005, 25 genes had been associated with asthma in six or more separate populations, including GSTM1 , IL10 , CTLA-4 , SPINK5 , LTC4S , IL4R and ADAM33 , among others.  Many of these genes are related to the immune system or modulating inflammation. Even among this list of genes supported by highly replicated studies, results have not been consistent among all populations tested.  In 2006 over 100 genes were associated with asthma in one genetic association study alone;  more continue to be found. 
Steroid induced diabetes can be a potential side effect of long term steroid use. But not always. Typically asthmatics that end up with steroid induced diabetes are most often those who are on very high doses of steroids over a long period of time due to uncontrolled severe asthma. Prednisone induces elevated glucose levels by stimulating glucose secretion by the liver. For many, it won’t raise it enough to lead to hyperglycemia.
As with most medications used in the treatment with asthma, they come with potential side effects. Some of those side effects are less desirable than others unfortunately. Talking with your doctor about the risk factors surrounding steroid induced diabetes would be a great place to start. For me personally, I’m a lifelong severe asthmatic and I’ve been taking both inhaled and oral steroids for most of my life and thankfully I have never had an issue with diabetes.
"For years I had been a "junkie"--addicted to prescription and over the counter drugs. used oral and topical anti-inflammatory corticosteroids for 9 years to suppress my eczema/psoriasis. The steroids' side effect nearly killed me and did nothing to cure my eczema. Why elimination or suppression of the symptom is NOT the same as elimination of the disease . The side effects caused me to swell-up like a balloon and triggered terrible mood swings from deep depression to nasty outburst our rages. Functioning of vital organs such as my liver, kidneys, lungs and spleen were nearly shut down and I thought I would die." Shirley