Yes, could be longer. The 21 day curve (peak at about 5-6 days) is from Africa where their general health is different, and possibly compromised. The other factor is that 13% of the people don’t present a fever but get sick and show the other symptoms. We can’t be sure about anything, but we can get lucky and I think the family got lucky.
I think the young step daughter helped their luck. She seemed to be somewhat sensible, in that she stopped the ambulance crew and told them to go back and get some protection.
She also apparently did some disinfection. I suspect that the family was also wary and perhaps avoided close contact after he became symptomatic, but who knows?