“Sneezing in response to either sexual ideation or after orgasm is an under-reported phenomenon, and may be much more common than expected” Read more about this phenomenon here: http://www.ncbi.nlm.nih.gov/pmc/articles/PMC2625373/?tool=pubmed
Of course this might as well don't have genetic factors at all, but could be a nice little study.
1. induced by sexual ideation AND orgasm
2. induced by sexual ideation ONLY
3. induced by orgasm ONLY
4. no response