Thanks, I think you nailed it. Funny how the reporter and the families involved don't mention this (...seems fairly... uhh... significant...).
Few people who had cases of smallpox as severe as Washington’s even survived, so it is highly probable that there were long-term effects and sterility is right at the top of the list.
Also, a person of Washington’s social status (and he was VERY conscious of this) would do everything possible to produce a male heir. Martha Custis was twenty-seven when she married George Washington, she had already had four children and had no known medical problems after this, so it is a virtual certainty that she was fertile. The only real logical conclusion is that George Washington was sterile.