Hmm DP rides a LOT and we have 2 girls - no trouble concieving them either, first try both times!
Thinking of all the other full on cyclists that we know there does seem to be a larger number of daughters in the group..... might get DP to do a poll with his bicycle forum and I will report the results back
OMG I would laugh if our DHs use the same bike forum! Your family did spring to mind as I was running through everyone I knew.