Well, honey, two Friday the 13th's in a row can happen once a year if the year starts on a Thursday. So, technically, it's possible, but it's about as rare as finding a unicorn at a yard sale. So, don't hold your breath waiting for that double dose of bad luck.
11/13 = 22/26 = 33/39
Three is the maximum and they have to fall in February, March and November as they do in 2009 (in leap years the max is still three, but the months are January, April, and July as in 1984 and 2012) . A normal year will have only one or two. The most is three. The least is one.
Tautology
1 in 36
0.149